JPH10178418A - Optical time division demultiplexer, demultiplex signal changeover method and optical time division multiplex system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To conduct optical time division multiplex processing in the optical time division demultiplexer while compensating a drift at an operating point as to the optical time division multiplex signal. SOLUTION: The optical time division demultiplexer 1 is provided with a clock signal generating section 2 that generates a clock signal for optical time division demultiplexing processing for a received optical signal and with an optical switch 3 applying time division demultiplexing to the optical signal based on the clock signal, and with an operating point stabilizing control circuit 4 in which a prescribed low frequency signal set in advance is superimposed on the clock signal for the optical time division demultiplexing fed to the optical switch 3, and the clock signal fed to the optical switch 3 and which controls the clock signal fed to the optical switch 3 so that the operating point on the operating characteristic of the optical switch 3 is made constant based on the phase difference between the prescribed low frequency signal component in the optical signal after optical time division demultiplexing processing by the optical switch 3 and the set prescribed low frequency signal component.

Description

DETAILED DESCRIPTION OF THE INVENTION

(Contents) Technical field to which the invention pertains Prior art (FIGS. 32 to 39) Problems to be solved by the invention (FIG. 39) Means for solving the problems (FIGS. 1 to 3) Embodiment-Description of the first embodiment (Figs. 4 to 6)-Description of the second embodiment (Fig. 7)-Description of the third embodiment (Fig. 8)-Description of the fourth embodiment (Figs. 9 to 11)・ Description of the fifth embodiment (FIGS. 12 and 13) ・ Description of the sixth embodiment (FIG. 14) ・ Description of the seventh embodiment (FIGS. 15 and 16) ・ Description of the eighth embodiment (FIG. 17) , Fig. 18)-Description of the ninth embodiment (Figs. 19, 20)-Description of the tenth embodiment (Fig. 21)-Description of the eleventh embodiment (Figs. 22, 23)-Description of the twelfth embodiment (FIGS. 24 and 25) ・ Description of the thirteenth embodiment (FIGS. 26 to 28) ・ Description of the fourteenth embodiment (FIGS. 29 to 3) 1) ・ Other effects of the invention

[0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical time division demultiplexing apparatus, a separation signal switching method, and an optical time division multiplex transmission system suitable for use in an optical communication system employing an optical time division multiplex transmission system.

[0003]

2. Description of the Related Art In recent years, with the rapid increase in the amount of information, it has been desired to increase the capacity of optical communication systems. At present, an optical amplification multiplex relay system with a transmission speed of 10 Gb / s (gigabit / second) is in the stage of practical use.
In such a relay system, further increase in capacity is expected, and therefore, it is necessary to develop an optical communication system in which the transmission speed is further increased.

In a conventional large-capacity optical communication system,
The mainstream has been to increase the capacity by increasing the speed of the electronic circuit for both the transmission unit and the reception unit. However, in recent years, it has become difficult to increase the speed of electronic circuits. For example, Si, GaAs, HB currently under research and development
It is said that the electric device for optical communication using T, HEMT, etc. is currently at a practical level up to 10 Gb / s.

In order to increase the transmission speed of the optical transmission system above the operation speed of the electronic device, it is considered effective to perform multiplexing and demultiplexing in the optical domain. Specifically, there are multiplexing and demultiplexing methods on the optical wavelength axis and bit multiplexing and demultiplexing methods on the time axis. In recent years, various technologies related to multiplexing and demultiplexing using these methods have been developed. R & D is being actively conducted.

FIG. 32 shows an optical time division multiplexing / demultiplexing method (optical time division multiplexing / demultiplexing) for performing bit multiplexing / demultiplexing on the time axis.
FIG. 33 is a block diagram showing an optical transmission / reception system (optical time division multiplex transmission system) 100 employing ion multiplexing (OTDM). The optical transmission / reception system 100 shown in FIG.
In the above, a signal sequence (hereinafter simply referred to as a sequence) constituting an optical time-division multiplexed signal is a bit multiplexed /
Separation is performed. It should be noted that a multi-system of three or more systems can be configured according to the optical transmission / reception system shown in FIG.

Here, in the optical transmission / reception system 100 shown in FIG. 32, an optical transmitter 102 and an optical receiver 103 are transmitted via a transmission line 101 constituted by an optical fiber or the like.
And are connected. Further, the optical transmitter 102 includes two optical modulators 104 and 105 and an optical time division multiplexing unit 106, and data signal information (B gigabit / second) modulated independently by the two optical modulators 104 and 105, respectively. The optical time division multiplexing unit 106 performs optical time division multiplexing on an optical signal including, for example, 20 Gb / s) so that 2 ×
The signal is transmitted via the transmission line 101 as an optical time division multiplexed signal (OTDM signal) of B gigabit / second (for example, 40 Gb / s).

The above-mentioned optical transmitter 102 is, for example, a laser diode 106a, as shown in FIG.
Modulating section 106b, oscillator 106c, branching section 106d, delay section 106e, modulating sections 106f and 106g, and multiplexing section 1
06h. Here, the laser diode 106a has a CW light (Carrier Wave;
(A constant level of light).
b is the excitation light from the laser diode 106a,
The modulation is performed by a clock signal having a frequency of 20 GHz from the oscillator 106c.

[0009] Further, the branching unit 106d includes a modulating unit 106d.
The optical signal in which the clock signal component of 20 GHz is modulated in b.
Is to delay one optical signal branched by the branching unit 106d by, for example, a half cycle of a 20 GHz clock signal. The modulation units 106f and 106g are:
At different timings, the clock light pulse modulated by the light modulator 106c is converted into data (for example, data having a transmission speed of about 20 Gb / s).
And output as an RZ (Return-to-Zero) optical signal.

For example, the modulation section 106f is
At the timing when the clock pulse in the optical signal from e rises, modulation is performed using an electric input signal of 20 Gb / s.
At the timing when the clock pulse of the optical signal itself branched in 6d rises, 20G independent from the above
The modulation is performed using an electrical input signal of b / s.

Further, the multiplexing unit 106h is connected to each modulation unit 10h.
By multiplexing optical signals (data of 20 Gb / s) modulated at different modulation timings at 6f and 106g, an optical signal can be output at a transmission speed of 2 × 20 Gb / s.

The optical receiver 103 of the optical transmission / reception system 100 shown in FIG.
UX (Demultiplex) 108, 109 and identification unit 110,
111. Here, the optical branching unit 1
07 is an optical time division multiplexed signal (2 ×
B gigabit / second, for example, 40 Gb / s).
1, and the received optical signal is power-branched into two. Each of the two optical time-division multiplexed signals is output to two optical DEMUXs 108 and 109. .

The optical DEMUXs 108 and 109 are modulated by the optical modulator 104 or the optical modulator 105 by modulating the optical time division multiplexed signals split by the optical splitter 107 at different timings. And outputs the separated signals. By the way, each of the optical DEMUXs 108 and 109 described above is a one-input one-output (1 × 1) Mach-Zehnder optical switch 112 and an optical switch 11 as shown in FIG.
Although a drive circuit 113 for supplying a drive voltage to the drive circuit 2 can be provided, a one-input one-output electroabsorption switch can be used in addition to the Mach-Zehnder switch 112.

Here, in the optical switch 112, a waveguide which is formed so as to be once branched and then coupled to each other is formed, while an electrode for applying a driving voltage is provided on the two branched waveguides. 112a and 112b are provided.
Accordingly, the optical signal input to the optical switch 112 is
The light is branched on the waveguide, passes through a waveguide having an electric field by a drive voltage described later, and is multiplexed at a coupling portion and output.

Further, in the driving circuit 113, a clock signal corresponding to the frequency of the clock signal generated by the oscillator 106c in the optical time division multiplexing unit 106 on the transmitting side is input, and based on this clock signal, the electrodes 112
a, 112b are supplied with mutually inverted (complementary) drive voltages. Specifically, FIG.
As shown in FIG.
By supplying the mutually inverted (complementary) drive voltages b and c to each of the optical signals a and 112b, one of the two signals constituting the input optical time division multiplexed signal a is separated. d can be output.

If the driving voltage supplied to the electrode 112a is a driving voltage c and the driving voltage supplied to the electrode 112b is a driving voltage b, the two components constituting the optical time-division multiplexed signal a are obtained. The other separated optical signal d 'of the signals can be output. That is,
A drive voltage supplied to the electrode 112a of the optical switch 112 constituting the optical DEMUX 108 is referred to as a drive voltage b,
By setting the drive voltage supplied to the electrode 112b to the drive voltage c, the optical time division multiplexed signal a (40 Gb / s) input from the optical branching unit 107 is modulated by, for example, 20 Gb / It can be separated into optical signals having s data information (separated optical signals d).

Similarly, the drive voltage supplied to the electrode 112a of the optical switch 112 constituting the optical DEMUX 109 is set to the drive voltage c, and the drive voltage supplied to the electrode 112b is set to the drive voltage b. Part 107
From the optical time-division multiplexed signal a (40 Gb / s)
For example, it can be separated into an optical signal (separated optical signal d ′) having data information of 20 Gb / s modulated by the modulator 105.

The optical time-division multiplexed signal a shown in FIG. 35 has a NRZ (Non-Return-to-Zero) waveform. In the optical DEMUXs 108 and 109, the optical pulse waveform is The same light separation operation is performed in the case of the included RZ waveform. Further, the identification unit 110 shown in FIG. 32 identifies the optical signal separated by the optical DEMUX 108 as actual data information. Similarly, the identification unit 111 performs actual identification on the optical signal separated by the optical DEMUX 109. Is identified as data information.

Thus, in the optical receiver 103,
A 2 × B gigabit / second (eg, 40 Gb / s) optical time division multiplexed signal received via the transmission line 101 is separated into two original B gigabit / second (eg, 20 Gb / s) optical signals. Can be identified. Note that the optical transmitter for performing the optical time division multiplexing processing as described above includes FIG.
In addition to the optical transmitter 102, an optical transmitter employing a method of multiplexing an optical pulse signal obtained by modulating light from a short pulse light source can also be used.

An optical receiver 114 as shown in FIG. 36 can be used instead of the optical receiver 103 for separating the above-mentioned duplex optical signal. That is, the optical receiver 114 shown in FIG. 36 includes an optical DEMUX 115 and identification units 116 and 117. Here, the optical DEMUX 115 is an optical time-division multiplexed signal (2 × B gigabit / second, for example, 40 G) from the optical transmitter 102.
b / s) via the transmission line 101, and subjects the received optical signal to time-division separation processing. More specifically, as shown in FIG. 37, a one-input two-output (1 × 2) Mach-Zehnder The optical switch 118 may include a pattern optical switch 118 and a drive circuit 119 for supplying a drive voltage to the optical switch 118.

In the optical switch 118, a waveguide is formed such that an input optical signal is split into two and output two, while a drive voltage is applied to the split waveguide. Electrodes 118a and 118b to be supplied are provided. As a result, the optical signal input to the optical switch 118 is branched on the waveguide and is output twice after passing through the waveguide having the electric field given by the drive voltage.

Further, in the driving circuit 119, similarly to the driving circuit 119 shown in FIG. 34 described above, a clock signal corresponding to the frequency of the clock signal generated by the oscillator 106c in the optical time division multiplexing unit 106 on the transmitting side is transmitted. Input and based on this clock signal, the electrodes 118a, 11
8b are supplied with mutually inverted drive voltages.

Thus, for example, as shown in FIG.
In the drive circuit 119, the drive voltages b and c inverted from each other are supplied to each of the electrodes 118a and 118b to separate one of the two signals constituting the input optical time division multiplexed signal a. An optical signal d (for example, an optical signal having data information modulated by the optical modulator 104) is output from one output port, and the other separated optical signal e (for example, the data information modulated by the optical modulator Optical signal) can be output from the other output port e.

Incidentally, the identification unit 116 shown in FIG.
The separated optical signal d is input from one output port of the optical DEMUX 115, and the separated optical signal d is identified as actual data information. Similarly, the identification unit 1
Reference numeral 17 is used to receive the separated optical signal e from the other output port of the optical DEMUX 115 and identify the separated optical signal e as actual data information.

Thus, also in the optical receiver 114,
A 2 × B gigabit / second (eg, 40 Gb / s) optical time division multiplexed signal received via the transmission line 101 is separated into two original B gigabit / second (eg, 20 Gb / s) optical signals. Can be identified. By the way, the Mach-Zehnder type optical switches 112 and 11 used in the optical transmitter 102 and the optical receivers 103 and 114 described above.
In No. 8, the power of the output light has a characteristic as shown by a solid line A in FIG. 39 with respect to the potential difference of the drive voltage applied complementarily to the two electrodes.

In this case, the amplitude of the pulse signal given by the drive circuit is such that "0" (minimum output) and "1" (maximum output) on the operating characteristic curve of the optical output intensity reciprocate. A potential difference is set. Specifically, as a pulse signal given by the drive voltage, Vb1
And Vb2 can be given an amplitude such that they reciprocate, and Vb2 and Vb3 can be given an amplitude such that they reciprocate.

[0027]

However, in the optical transmitting / receiving system 100 employing the optical time division multiplexing as shown in FIG. 32, the optical DEMUX in the receiver is used.
The Mach-Zehnder optical switch 112 is used for 108 and 109.
There is a problem that the operating point drifts due to a temperature change or a change over time due to the influence of the lithium niobate configuration that constitutes the above.

That is, by giving an amplitude such that Vb1 and Vb2 shown in FIG. 39 reciprocate as shown in FIG. 39, the output intensity of the optical switch becomes "0" (minimum output) on the operation characteristic curve. Despite the setting so that “1” and “1” (maximum output) reciprocate, the operating characteristic curve is changed by the dotted line (B) in FIG.
Or it moves like the dotted line (C).

In this case, the potential difference such that "0" (minimum output) and "1" (maximum output) reciprocate on the operating characteristic curve of the optical output intensity changes (the operating point drifts). If the amplitude is such that Vb1 and Vb2 reciprocate, sufficient light output intensity cannot be obtained. Further, in the optical transmitting / receiving system 100 employing the optical time division multiplexing shown in FIG.
In the optical DEMUX of the receiver, by performing optical time-division separation processing on the received optical signal, a bit string on the side required by the receiver side is extracted, but the bit string may be changed as necessary. It is necessary to perform the switching efficiently while considering the above-mentioned operating point drift.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has been made in consideration of such a problem. An optical time division multiplex signal can be subjected to optical time division demultiplexing while compensating for operating point drift. It is an object to provide a demultiplexer and an optical time division multiplex transmission system. Another object of the present invention is to provide a separation signal switching method capable of efficiently switching a bit string that can be extracted according to a request of a receiver.

[0031]

FIG. 1 is a block diagram showing the principle of the present invention, and an optical time division demultiplexing apparatus 1 shown in FIG.
It comprises a clock signal generator 2, an optical switch 3, and an operating point stabilization control circuit 4. That is, the clock signal generation unit 2 generates a clock signal for optical time division separation processing of the received optical signal, and the optical switch 3 generates an optical signal based on the clock signal from the clock signal generation unit 2. Are separated by time division.

Further, the operating point stabilization control circuit 4 superimposes a predetermined low-frequency signal on a clock signal for optical time division separation supplied to the optical switch 2, and controls the optical switch 2. The operating point of the clock signal supplied to the optical switch is determined based on the phase difference between the predetermined low-frequency signal component in the optical signal after the time-division separation processing and the set predetermined low-frequency signal component. Is controlled so as to be at a fixed position with respect to the operation characteristics of the first embodiment (claim 1).

Here, the above-mentioned operating point stabilization control circuit 4
A low-frequency oscillator that generates a predetermined low-frequency signal, and the low-frequency signal from the low-frequency oscillator superimposed on the clock signal from the clock signal generation unit 2 as a clock signal for the optical switch 3. A low-frequency superimposing unit for outputting, a low-frequency signal detecting unit for detecting the low-frequency signal included in the optical signal time-division-divided by the optical switch 3,
A bias voltage supply unit that applies a bias voltage corresponding to a difference between the phase of the low frequency signal from the low frequency oscillator and the phase of the low frequency signal detected by the low frequency signal detection unit to the optical switch 3 (Claim 2).

FIG. 2 is also a block diagram showing the principle of the present invention. The optical time division demultiplexer 5 shown in FIG. 2 also includes a clock signal generator 6, optical switches 7-1 to 7-1, and
-N (n; integer of 2 or more) and operating point stabilization control circuit 8
It is configured with. Here, the clock signal generation unit 6 generates a clock signal for optical time division separation processing of the received optical signal, and each of the optical switches 7-1 to 7-n.
Is for time-division separation of an optical signal based on the clock signal from the clock signal generator 6. That is, the optical switches 7-1 to 7-n are connected in a plurality of stages so that an input optical signal can be subjected to time-division separation a plurality of times.

Further, the operating point stabilization control circuit 8 applies a predetermined low frequency signal to the clock signal for optical time division separation processing supplied to each of the optical switches 7-1 to 7-n. The optical switches 7-1 to 7-n
Operating point of the clock signal supplied to each optical switch based on the phase difference between the predetermined low-frequency signal component in the optical signal after the time-division separation processing and the predetermined low-frequency signal component set in the optical signal. Performs control so that the operating characteristics of the optical switches 7-1 to 7-n are kept at a fixed position (claim 3).

The above-mentioned operating point stabilization control circuit 8 is
Each of the optical switches 7-1 to 7-n may include a low-frequency oscillator, a low-frequency superimposing unit, a low-frequency signal detecting unit, and a bias voltage supplying unit. Here, the low-frequency oscillator generates predetermined low-frequency signals different from each other, and the low-frequency superimposing unit applies a predetermined low-frequency signal from the low-frequency oscillator to the clock signal from the clock signal generation unit 6. Superimposed and output as a clock signal to the optical switch 7-i (i; any integer from 1 to n);
The low-frequency signal detector detects the low-frequency signal from the optical signal output from the last-stage optical switch 7-n.

The bias voltage supply section supplies a bias voltage corresponding to a difference between the phase of the low frequency signal from the low frequency oscillator and the phase of the low frequency signal detected by the low frequency signal detection section to an optical signal. This is applied to the switch 7-i (claim 4). Further, the above-mentioned operating point stabilization control circuit 8 includes a low frequency oscillator, a low frequency signal detecting section, a phase difference detecting section, a low frequency superimposing section, a bias voltage supply holding section, a first switch and a second switch. It can also be configured.

Here, the low-frequency oscillator generates a predetermined low-frequency signal, and the low-frequency signal detector detects the low-frequency signal from the optical signal output from the last-stage optical switch 7-n. The low-frequency signal is detected, and the phase difference detection unit detects the phase difference between the phase of the low-frequency signal from the low-frequency oscillator and the low-frequency signal detected by the low-frequency signal detection unit. is there.

A low-frequency superimposing section is provided for each of the optical switches 7-1 to 7-n at the respective stages, and adds the low-frequency signal from the low-frequency oscillator to the clock signal from the clock signal generating section 6. The bias voltage supply holding unit is provided for each of the optical switches 7-1 to 7-n in each of the above stages, and supplies a bias voltage according to phase difference detection information from the phase difference detection unit. The holding is held once.

Further, the first switch selectively switches and outputs the low-frequency signal from the low-frequency oscillator to one of the low-frequency superimposing sections in each stage.
The second switch selectively switches and outputs the phase difference detection information from the phase difference detection unit to one of the bias voltage supply and holding units in each stage. Further, the operating point of the clock signal supplied to any of the plurality of optical switches 7-1 to 7-n is changed to the optical switches 7-1 to 7-n.
In order to switch the control to be a fixed position with respect to the operating characteristics of 7-n, the switching of the first switch and the second switch is controlled, and the bias held by the bias voltage supply holding unit is held. Updating of the voltage information is controlled (claim 5).

FIG. 3 is a block diagram showing the principle of the present invention. The optical time division demultiplexer 9 shown in FIG. 3 includes a clock signal generator 10, a first optical demultiplexer 11, and an optical switch 12-.
1 to 12-n, optical multiplexing unit 13, operating point stabilization control circuit 1
4 is provided. Here, the clock signal generator 10 generates a clock signal for optical time division separation processing of the received optical signal, and the first optical separator 11 separates the input signal light into a plurality of optical signals. It is.

Each of the optical switches 12-i (i; 1 to n)
Is an integer of any one of the above), the respective optical signals separated by the first optical demultiplexing unit 11 are time-division-separated based on the clock signal. The optical signals that are time-divisionally separated by the switches 12-1 to 12-n are multiplexed. Further, the operating point stabilization control circuit 14 superimposes a predetermined low frequency signal on the clock signal for optical time division separation supplied to each optical switch 12-i, Operating point of the clock signal supplied to each optical switch based on the phase difference between the predetermined low-frequency signal component in the optical signal after the time-division separation processing and the predetermined low-frequency signal component set in the optical signal. Performs control so as to be at a fixed position with respect to the operation characteristics (claim 6).

Here, the above-mentioned operating point stabilization control unit 14
Comprises a low-frequency oscillator, a low-frequency superimposing unit, a low-frequency signal detection unit, and a bias voltage supply unit for each optical switch 12-i. Here, the low-frequency oscillator generates predetermined low-frequency signals different from each other, and the low-frequency superimposing unit superimposes the predetermined low-frequency signal from the low-frequency oscillator on the clock signal from the clock signal generating unit 10. The low-frequency signal detection section detects the low-frequency signal from the optical signal multiplexed by the optical multiplexing section 13.

Further, the bias voltage supply section supplies a bias voltage corresponding to the difference between the phase of the low frequency signal from the low frequency oscillator and the phase of the low frequency signal detected by the low frequency signal detection section to an optical signal. This is applied to the switch 12-i (claim 7). The operating point stabilization control unit 14 includes a low frequency oscillator, a low frequency signal detection unit, a bias voltage supply unit, a low frequency superposition unit, a bias voltage holding unit, a first switch, and a second switch. It can also be configured.

Here, the low-frequency oscillator generates a predetermined low-frequency signal, and the low-frequency signal detector detects the low-frequency signal from the optical signal multiplexed by the optical multiplexing unit 13. And a bias voltage supply unit configured to detect a bias voltage corresponding to a difference between a phase of the low frequency signal from the low frequency oscillator and a phase of the low frequency signal detected by the low frequency signal detection unit. To the optical switches 12-1 to 12-
n.

Further, a low frequency superimposing section is provided for each of the plurality of optical switches 12-1 to 12-n, and the low frequency signal from the low frequency oscillator is added to the clock signal from the clock signal generating section 10. They are superimposed. The bias voltage holding unit includes the plurality of optical switches 12-1 to 12-n.
It is provided for each and temporarily holds the bias voltage information from the bias voltage supply unit.

Further, the first changeover switch selectively switches the low-frequency signal from the low-frequency oscillator to any one of a plurality of low-frequency superimposing sections and outputs the same.
The second switch selectively switches the bias voltage from the bias voltage supply unit to any one of the plurality of bias voltage holding units and outputs the same. Also,
The bias from the bias voltage supply unit is set such that the operating point of the clock signal supplied to any of the plurality of optical switches 12-1 to 12-n is at a fixed position with respect to the operating characteristics of the optical switch. The switching of the first switch and the second switch is controlled so that the voltage is supplied, and the bias voltage information from the bias voltage holding unit is updated (claim 8).

Further, the first optical demultiplexing unit 11 can be configured to demultiplex a wavelength-multiplexed component in the input signal light (claim 9), and also to separate a two-polarized component in the input signal light. (Claim 10). In this case, a second optical separation unit that separates two polarization components in the optical signal multiplexed by the optical multiplexing unit 13 is interposed between the optical multiplexing unit 13 and the low-frequency signal detection unit. (Claim 11).

In the optical time division demultiplexing devices 1, 5 and 9 of the present invention shown in FIGS. 1 to 3, the bias voltage supply sections in the operating point stabilization control circuits 4, 8 and 14 are replaced by the low frequency oscillator. The drift of the operating characteristics of the optical switch is detected based on the difference between the phase of the low-frequency signal from the optical switch and the phase of the low-frequency signal detected by the low-frequency signal detector. -N, 12-1 to 12-n may be configured to supply a bias voltage such that the operating point of the clock signal supplied to the operating characteristic is at a fixed position with respect to the operating characteristics.

In this case, the optical switch 3 is controlled based on the difference between the phase of the low-frequency signal detected by the low-frequency signal detector and the phase of the low-frequency signal from the low-frequency oscillator. , 7-1 to 7-n, 12-1 to
A drift detector for detecting the drift of the 12-n operating characteristic, and a bias voltage corresponding to the drift detected by the drift detector are supplied to the optical switches 3, 7-1 to 7-n, 1
It is also possible to provide a bias voltage applying unit that applies the clock signal superimposed on the clock signal supplied to 2-1 to 12-n (claim 12).

In the optical time division demultiplexing devices 1, 5 and 9 of the present invention shown in FIGS.
7-n and 12-1 to 12-n, a branching unit for branching the optical signal output from the branching unit, and a photoelectric conversion unit for converting the optical signal branched by the branching unit into an electric signal. The signal detection unit can be configured by a band-pass filter that can pass a predetermined low-frequency component in the electric signal from the photoelectric conversion unit (claim 13).

Further, in the optical time division demultiplexing devices 1, 5 and 9 of the present invention shown in FIGS.
1 to 7-n and 12-1 to 12-n, it is also possible to provide an extraction bit string switching unit for switching the bit string to be extracted after time division separation (claim 15). Switch 3, 7-1
7-n, and 12-1 to 12-n, the operating points on the operating characteristics may be shifted by a half cycle (claim 16).

Further, as the above-mentioned extracted bit string switching unit, the components of the clock signal from the clock signal generation units 2, 6, and 10 are changed to change the optical switches 3, 7-1 to 7-.
n, 12-1 to 12-n. In this case, the clock variable section can be configured to be capable of inverting the clock signal from the clock signal generation sections 2, 6, and 10 (claim 18), and besides the clock signal generation sections 2, 6 , 10 can be delayed by a half cycle.
9).

Further, as the above-mentioned extracted bit string switching unit, the optical switches 2, 7-1 to 7-n, 12-1 to 12-
An optical path length changeover switch which can be switched to an optical path inserted before n to change the optical path length of the input optical signal by one time slot can be used.
0). In the optical time division demultiplexing devices 1, 5, and 9 of the present invention shown in FIGS. 1 to 3 described above, the optical switches 3, 7-1 to 7-
n, 12-1 to 12-n can be constituted by a one-input one-output Mach-Zehnder type optical switch (claim 21), and can also be constituted by a one-input two-output Mach-Zehnder optical switch (claim). Item 22).

Further, according to the separation signal switching method of the present invention, in a plurality of optical switches, the
In the separation signal switching method for switching signals to be output in a time-division manner when performing optical-time-division separation based on a clock signal, the time-division separation is performed when a bit string to be taken out by time-division separation is switched by an optical switch. The phase of the clock signal input to the other optical switch is shifted by a desired amount in synchronization with the switching timing of the optical signal.

In the separation signal switching method of the present invention, when an input optical signal is optically time-division-separated by an optical switch and then converted into an electric signal, and further, the time-division separation is electrically performed based on a clock signal. In the separated signal switching method for switching signals to be output in a time-division manner, when the bit sequence to be extracted by the optical time-division switching is switched by the optical switch, the electrical time is synchronized with the switching timing of the extracted bit sequence. It is characterized in that the phase of the clock signal at the time of dividing and separating is shifted by a desired amount.

Further, according to the separation signal switching method of the present invention, after the input optical signal is optically time-division-separated by an optical switch and converted into an electric signal, when the data is identified by the identification clock, the time-division separation is performed. In the separation signal switching method for switching the signal to be identified, when the optical signal to be time-division separated by the optical switch is switched, the phase of the identification clock is changed by a desired amount in synchronization with the switching timing of the optical signal to be time-division separated. It is characterized in that it is shifted (claim 25).

The optical time-division multiplexing transmission system of the present invention further comprises a pumping light source for outputting pumping light, a low-frequency oscillator for generating a predetermined low-frequency signal, and a low-frequency oscillator for an input clock signal. A low-frequency superimposing unit that superimposes the low-frequency signal from the excitation light from the excitation light source, based on the clock signal on which the low-frequency signal is superimposed by the low-frequency superimposing unit, performing time-division multiplexing modulation An optical switch to transmit, and a low-frequency signal detection unit that detects the low-frequency signal included in the optical signal time-division multiplexed by the transmission-side optical switch,
A bias voltage supply unit that applies a bias voltage corresponding to a difference between the phase of the low-frequency signal from the low-frequency oscillator and the phase of the low-frequency signal detected by the low-frequency signal detection unit to the optical switch; With an optical time-division multiplexing device having a clock signal generation unit that generates a clock signal for optical time-division separation processing of a received optical signal, and a low-frequency oscillator that generates a predetermined low-frequency signal set in advance, A low-frequency superimposing unit that superimposes the low-frequency signal from a low-frequency oscillator on a clock signal from a clock signal generating unit; and An optical switch for time-division separation of an optical signal,
A low-frequency signal detection unit for detecting the low-frequency signal included in the optical signal time-division separated by the optical switch, and a phase of the low-frequency signal from the low-frequency oscillator and detected by the low-frequency signal detection unit An optical time-division separating device having a bias voltage supply unit for applying a bias voltage corresponding to the phase difference of the low frequency signal to the optical switch is provided. ).

[0059]

Embodiments of the present invention will be described below with reference to the drawings. (A) Description of First Embodiment FIG. 4 is a block diagram showing an optical time division demultiplexer according to a first embodiment of the present invention. The optical time division demultiplexer shown in FIG. The optical DEMUX 108, 109 in the optical receiver 103 shown in FIG.
08, 109).

In other words, in the first embodiment, an optical receiver is configured by arranging the optical DEMUX 20 at the position of the optical DEMUX 108, 109. Note that, as in the case of FIG.
Each light D placed at the position of UX108, UX109
The EMUX 20 separates and outputs signals of different sequences by modulating the optical time-division multiplexed signals split by the optical splitter 107 with different timings.

Thus, as in the case of FIG. 32 described above, the optical receiver 103 having the optical DEMUX 20 as the optical DEMUXs 108 and 109 also has the transmission path 101.
2 × B gigabits per second (e.g., 40
(Gb / s) optical time-division multiplexed signal can be separated and identified as the original two types of B gigabit / second (for example, 20 Gb / s) optical signals.

Here, the optical DEMUX 20 shown in FIG.
Comprises a clock signal generating unit 21, an optical switch 22, a low frequency oscillator 23, a low frequency superimposing unit 24, an optical branching unit 25, a light receiver 26, a band pass filter 27, and a phase detection / bias supply circuit 28. I have. The clock signal generator 21 generates a clock signal for optical time division separation processing of a received optical signal. Specifically, the modulation unit 10 in the optical time-division multiplexing unit 106 on the transmission side converts the received optical signal.
6b (see FIG. 33), a clock signal component modulated is extracted, and a clock signal for the optical time division separation process is generated from the clock signal component.

The optical switch 22 is composed of a 1 × 1 Mach-Zehnder type optical switch, as in the case of FIG. 34 described above, and generates an optical signal based on the clock signal generated by the clock signal generator 21 described above. The 2 × B gigabit / second optical signal input from the branching unit 107 is subjected to time division separation processing and output as a B gigabit / second optical signal, and includes electrodes 22a and 22b for receiving a drive voltage. (Hereinafter, a Mach-Zehnder optical switch is simply referred to as an optical switch).

For example, in this optical switch 22,
The optical time division multiplexed signal of 2 × B gigabit / sec is separated and extracted every other bit based on the B gigahertz clock signal from the clock signal generator 21. Further, the low-frequency oscillator 23 generates a predetermined low-frequency signal f ₀ , and the drive circuit 24 receives the clock signal from the clock signal generator 21 and applies the clock signal to the electrodes 22a and 22b. A clock signal is generated as a drive signal to be supplied, and a low-frequency signal f from the low-frequency oscillator 23 is added to these clock signals.
₀ is superimposed, and two clock signals on which the low-frequency signal f ₀ is superimposed are output as drive signals for the electrodes 22a and 22b of the optical switch 22.

The two clock signals generated in the drive circuit 24 are two complementary clock signals generated based on the clock signal generated by the clock signal generation unit 21. The low frequency signal f ₀ from the low frequency oscillator 23 is superimposed on the clock signal and output to the optical switch 22.

Thus, each electrode 22 of the optical switch 22
In a and 22b, mutually complementary clock signals from the drive circuit 24 (the low-frequency signal f ₀ is superimposed).
Is input, and the received optical signal can be time-division-separated based on this clock signal. The optical branching unit 25 performs power branching on the optical signal time-division-divided by the optical switch 22, and the optical receiver 26 receives the branched optical signal from the optical branching unit 25 and converts it into an electric signal. And has a function as a photoelectric conversion unit.

Further, a band pass filter (BPF)
The filter 27 is capable of passing the low-frequency component f ₀ of the electric signal from the light receiver 26,
, The low frequency signal f ₀ included in the time-division separated optical signal
And has a function as a low-frequency signal detection unit. The phase detection and bias supply circuit 28 as a bias voltage supply unit, the difference between the low frequency signal f ₀ of the phase extracted by the phase and the band-pass filter 27 of the low-frequency signal f ₀ from the low frequency oscillator 23 Is applied to the optical switch 22.
Specifically, it has a configuration as shown in FIG.

Here, the phase detection / bias supply circuit 28 shown in FIG. 5 includes an inverted full-wave rectifier 28a and a low-pass filter 28b. The inverted full-wave rectifier 28a outputs the low-frequency signal f ₀ from the low-frequency oscillator 23.
Of the low-frequency signal f ₀ detected by the band-pass filter 27 (see FIG. 5), and the low-pass filter 28 b
The DC component is extracted by performing a low-pass filter process on the calculation result from the inverting full-wave rectifier 28a.

[0069] That is, the DC component output from the above-mentioned low-pass filter 28b is, the low-frequency signal f ₀ of the low-frequency signal f ₀ of the phase detected by the phase and the band-pass filter 27 from the low frequency oscillator 23 Drift detection information based on the difference can be used, and a bias voltage corresponding to the DC component drift is output by being superimposed on the clock signal from the drive circuit 24 described above.

When the operating point drift does not occur in the optical switch 22, the band-pass filter 27 causes the optical switch 22 to operate despite the low frequency signal f ₀ being superimposed by the driving circuit 24. since the frequency component f ₀ above from the output signal of the not detected, the DC component from the low-pass filter 28b is not detected, the optical switch 22
, No bias voltage is applied.

Therefore, the above-mentioned inverted full-wave rectifier 28a and low-pass filter 28b form the band-pass filter 27.
Phase of the low-frequency signal f ₀ detected by the
And a bias voltage corresponding to the detected drift is supplied to the optical switch 22 while functioning as a drift detection unit for detecting a drift in the operation characteristics of the optical switch 22 based on the phase difference of the low frequency signal f ₀ from the third switch. It functions as a bias voltage applying unit that applies the signal superimposed on the clock signal.

Thus, the above-described inverted full-wave rectifier 28a
And a low-frequency oscillator 23 by a phase detection / bias supply circuit 28 having a low-pass filter 28b.
The drift of the operating characteristics of the optical switch 22 is detected based on the difference between the phase of the low-frequency signal from the optical switch 22 and the phase of the low-frequency signal f ₀ detected by the band-pass filter 27, and is supplied to the optical switch 22. A bias voltage is supplied such that the operating point of the clock signal is at a fixed position with respect to the operating characteristics (automatic bias control, ABC control; Automatic Bias Con
trol).

Therefore, the above-mentioned low-frequency oscillator 23, drive circuit 24, optical splitter 25, light receiver 26, band-pass filter 27, and phase detection / bias supply circuit 28 cause the optical time division separation supplied to the optical switch 22. A predetermined low-frequency signal f ₀ is superimposed on the processing clock signal, and the low-frequency signal component f ₀ in the optical signal after the time-division separation processing by the optical switch 22 and the low-frequency signal superimposed on the clock signal are performed. The clock signal supplied to the optical switch 22 is converted to the optical switch 2 based on the phase difference with the component of the signal f _0.
An operating point stabilization control circuit 29 for controlling the operating point on the operating characteristic of No. 2 to be a fixed position is configured.

With the above configuration, in the optical time division demultiplexing apparatus according to the first embodiment of the present invention, for example, a 2 × B gigabit / sec time division multiplexed signal in which two series of optical signals from the transmitter 102 are multiplexed Is received, the optical DEMUX 108,
In the clock signal generator 21 of each optical DEMUX 20 arranged at the position 109, a clock signal for performing optical time division separation in the optical switch 22 from the time division multiplexed signal received by the receiver 103 (in this case, Produces B gigahertz).

Further, the drive circuit 24 generates two clock signals complementary to each other based on the clock signal from the clock signal generation unit 21, and applies these two clock signals to the low frequency signal from the low frequency oscillator 23. f ₀
And the electrodes 22a, 22a of the optical switch 22 are respectively superposed.
22b. In the optical switch 22,
The optical time-division multiplexed signal as a received optical signal input via the optical branching unit 107 is modulated by two clock signals for optical time-division separation processing generated by the drive circuit 24 to form a two-series signal. It is output as a separated signal of one of the series.

Here, as shown in FIG. 6, for example, in the drive circuit 24 of the optical DEMUX 20 described above, the two clock signals from the clock signal generator 21 are applied with the amplitude of the low frequency signal f ₀ from the low frequency oscillator 23. After the modulation (refer to the input electric signal (S1)), the two complementary clock signals subjected to the amplitude modulation processing are supplied to each electrode 22.
a, 22b.

Thus, the optical switch 22 outputs the separated signal under the influence of the amplitude modulation of the low-frequency signal f ₀ related to the clock signal. That is, when the optical switch 22 does not generate an operating point drift due to a change in temperature or a change with time, the potential difference between the drive voltage applied to the electrodes 22a and 22b of the optical switch 22 and the output optical power is not affected. The operation characteristic curve showing the relationship is shown in FIG.
Therefore, when (S1) is applied as a drive signal to the electrodes 22a and 22b, the output optical signal becomes as shown in (S4). That is, since the low-frequency signal f ₀ is superimposed on the drive signal, the output optical signal (S
In 4), the component of the frequency 2f ₀ remains and is output.

When an operating point drift occurs in the optical switch 22 and the operating characteristic curve shifts as shown in (S8), the output optical signal becomes as shown in (S2). That is, since the low frequency signal f ₀ is superimposed on the drive signal, the output optical signal (S2) is output including the component of the frequency f ₀ . Similarly, when an operating point drift occurs in the optical switch 22 and the operating characteristic curve shifts as shown in (S6), the output optical signal becomes as shown in (S3). That is, since the low-frequency signal f ₀ is superimposed on the drive signal, the output optical signal (S3) is output including the component of the frequency f ₀ .

In the optical branching unit 25, the optical switch 22
While branching the output optical signal from and outputting one of the branched optical signals to the subsequent identification unit 110 or identification unit 111;
The other output light signal is used as monitor light
After being converted into an electric signal, the electric signal is output to the band-pass filter 27. In the bandpass filter 27, the light receiving device 2
The frequency f ₀ component included in the output optical signal from the optical signal generator 6 is extracted. When the frequency f ₀ component is extracted by the band-pass filter 27, an operating point drift occurs, and the low-frequency signal f ₀ from the band-pass filter 27 and the low-frequency signal f ₀ The operating point drift is detected by comparing the phase of the low frequency signal f ₀ from the oscillator 23.

Further, the phase detection / bias supply circuit 28
, A DC bias voltage based on the amount of the operating point drift is generated, and the electrodes 22a and 22a of the optical switch 22 are generated.
2b is superimposed on the clock signal from the drive circuit 24 and output. Thereby, in the optical switch 22,
A DC bias voltage is applied to the clock signal as a drive signal in accordance with the detected operating point drift, and the optical switch 22 is controlled so that the operating point on the operating characteristics is at a fixed position.

The split optical signal output from the optical switch 22 to the identification section 110 or the identification section 111 via the optical splitting section 25 is identified as a separation signal. By the way, the output light intensity characteristic of the Mach-Zehnder type optical switch 22 depends on the potential difference between the drive signals supplied to the two electrodes 22a and 22b. Therefore, by adding signals whose polarities are inverted to each other to the two electrodes 22a and 22b. Two electrodes 22
The drive can be performed with half the electrical amplitude as compared with the case where a drive signal is applied to either one of a and 22b.

The electrode 22 of the optical switch constituting the optical DEMUX 20 disposed at the position of the optical DEMUX 108
a and 22b are supplied to the optical DE
If the corresponding clock signals supplied to the electrodes 22a and 22b of the optical switch constituting the optical DEMUX 20 arranged at the position of the MUX 109 are set to be inverted with respect to each other, the optical DEMUX 20 is arranged at the position of each optical DEMUX 108 and 109. In the optical DEMUX 20, an optical time-division multiplexed signal in which two series of optical signals are multiplexed can be separated into different series of optical signals (see d and d 'shown in FIG. 35).

As described above, according to the optical time division demultiplexing apparatus according to the first embodiment of the present invention, the operating point stabilization control circuit 2
9 superimposes a predetermined low-frequency signal f ₀ preset by the low-frequency oscillator 23 on the clock signal for optical time-division separation supplied to the optical switch 22, and performs time-division separation by the optical switch 22. A clock supplied to the optical switch 22 based on a phase difference between the above-described low-frequency signal f ₀ component in the processed optical signal and a predetermined low-frequency signal f ₀ component set by the low-frequency oscillator 23. Since the signal can be controlled so that the operating point on the operating characteristic of the optical switch 22 is at a fixed position, the optical time division multiplexing can be performed on the optical time division multiplexed signal while compensating the operating point drift. Therefore, there is an advantage that a separated signal having a sufficient light output intensity can be output.

(B) Description of the Second Embodiment The optical time division demultiplexing apparatus according to the first embodiment is applied to the optical transmission / reception system 100 shown in FIG. 1
09 is arranged as a light DEMUX 20. In other words, in the first embodiment, the optical receiver 1 in the optical time division multiplex transmission system is connected by connecting the optical DEMUX 20 as an optical time division demultiplexer in two stages in parallel.
03 is configured.

However, according to the present invention, by using the optical DEMUX having the same configuration as that of the optical DEMUX (see reference numeral 20) in the first embodiment, the optical transmission / reception can be performed by only one optical DEMUX 20 and the identification unit. By configuring an optical receiver in the system, or by connecting three or more optical DEMUXs 20 in parallel and providing identification units corresponding to the number of stages of the optical DEMUX 20 as shown in FIG. A receiver can also be configured.

FIG. 7 is a block diagram showing a main part of an optical receiver according to the second embodiment of the present invention.
The optical receiver 103A shown in FIG. 1 can separate three or more multi-series optical time division multiplexed signals as described above. The optical receiver 103A is configured according to the one shown in FIG. 32 (see reference numeral 103). That is, the optical receiver 103A according to the second embodiment includes an optical splitting / branching unit 107A and optical DEMUXs 30-1 to 30-m.
(M; an integer of 3 or more) and the optical DEMU
X30-1 to X30-m are provided for each optical DEMUX30.
It comprises an identification unit (not shown) for identifying the separated signals from -1 to 30-n.

Here, each of the optical DEMUXs 30-1 to 30-
m includes a clock signal generator 21, an optical switch 22, and an operating point stabilization control circuit 29 having substantially the same functions as those in the first embodiment. The drive circuit 24 in each of the optical DEMUXs 30-1 to 30-m supplies a drive signal to only one electrode of the optical switch 22. 7, the same reference numerals as those in FIG. 4 denote the same parts, and a detailed description thereof will be omitted.

With the above-described configuration, in the second embodiment of the present invention, when a time division multiplexed signal is received from a transmitter via a transmission line, the signal is split into m by the optical splitting unit 107A and split into optical DEMUXs 30-1 to 30-. m. Each light D
The clock signal generator 21 of the EMUX 30-i generates a desired clock signal for optical time division demultiplexing processing from the optical time division multiplex signal as the received optical signal, and the optical switch 22 inputs the input optical time division multiplex signal. The signal is modulated by the clock signal from the clock signal generator 21 to be output as a desired separated signal.

The separation signal output from the optical switch 22 is output to an identification unit (not shown) via the optical branching unit 25 and is identified as a separation signal. In addition, each optical DEM
In the UX 30-i, the operating point stabilization control circuit 29 performs the same operating point stabilization control as in the above-described first embodiment. That is, the low-frequency oscillator 2 is added to the clock signal for the optical time-division separation processing supplied to the optical switch 22.
Superimposing a prescribed low-frequency signal f ₀ set in advance by 3. Further, in the phase detection / bias supply circuit 28, the low frequency signal f ₀ component of the optical signal after the time-division separation processing by the optical switch 22 is converted into the optical branching unit 25
And a low-frequency signal f ₀ from the low-frequency oscillator 23 while being input through the band-pass filter 27.

Subsequently, the phase detection / bias supply circuit 28
Then, the phase of the low frequency signal f ₀ component in the optical signal after the time division separation processing by the optical switch 22 and the phase of the low frequency signal f ₀ from the low frequency oscillator 23 are compared, and the DC bias voltage based on the phase difference is calculated. , And is supplied in a manner superimposed on the drive signal for the optical switch 22. Thus, the clock signal supplied to the optical switch 22 is controlled so that the operating point on the operating characteristics of the optical switch 22 becomes a fixed position.

As described above, also in the second embodiment of the present invention, each optical DEMUX 30-
Since operating point stabilization control can be performed in the operating point stabilization control units of 1 to 30-m, similar to the case of the first embodiment, a desired operating point drift is compensated for the optical time division multiplexed signal while compensating the operating point drift. There is an advantage that the optical time division separation process can be performed while maintaining a sufficient light output intensity.

(C) Description of the Third Embodiment In the optical time division demultiplexing apparatus according to the first embodiment, a 1 × 1 Mach-Zehnder optical switch is used as the optical switch 22, but the present invention is not limited to this. FIG.
7 (see reference numeral 118), a 1 × 2 Mach-Zehnder optical switch 22A can be used.

That is, if a 1 × 2 Mach-Zehnder type optical switch is used as the optical switch 22A to constitute an optical time division demultiplexer, this optical time division demultiplexer is used as the optical DEMUX 115 of the optical receiver 114 shown in FIG. Application (Light D
(Disposed at the position of the EMUX 115). Here, FIG. 8 shows light D as an optical time-division demultiplexing device 20A to which the above-described 1 × 2 Mach-Zehnder optical switch is applied.
FIG. 39 is a block diagram showing an EMUX. The optical DEMUX 20A shown in FIG. 8 is replaced with the optical DEMUX shown in FIG.
115, the optical DEMUX2
The optical receiver in the optical time-division multiplex transmission system can be configured by the 0A and the identification units 116 and 117.

Here, in the optical switch 22A of the optical DEMUX 20A, similarly to the optical switch 22A shown in FIG. 37, a waveguide is formed such that an input optical signal is split into two and then output. On the other hand, the two branched waveguides are provided with electrodes 22a and 22b to which a drive voltage is supplied. As a result, the optical signal input to the optical switch 22A is split on the waveguide and is output twice after passing through the waveguide having the electric field given by the drive signal.

The optical DEMUX 20A shown in FIG.
Also includes an operating point stabilization control circuit 29A as in the case of the above-described first embodiment. FIG.
Here, the same reference numerals as those in FIG. 4 denote substantially the same parts, and a detailed description thereof will be omitted. Here, the drive circuit 24A receives the clock signal for optical time division separation processing generated by the clock signal generation unit 21, and based on this clock signal, complements each other as a drive signal for each of the electrodes 22a and 22b. To generate two clock signals for the optical switch 2
In 2A, it is possible to output two separated optical signals of two input optical signals constituting the input optical time division multiplexed signal.

[0096] Incidentally, as in the first embodiment described above, the two clock signals generated by the driving circuit 24A is also a low-frequency signal f ₀ is superimposed optical switch from 22A from the low frequency oscillator 23 It is supplied to. By the way, two complementary signals are output from the optical switch 22A. In this case, it is not necessary to split both of the two optical outputs for feedback control for operating point stabilization control. Only one of the two light outputs may be used. In particular, when only one signal is used for identification on the receiving side, the other signal can be used only for operating point stabilization control without optical separation.

With the above configuration, in the third embodiment of the present invention, if the optical DEMUX 20A shown in FIG. 8 is arranged at the position of the optical DEMUX 115 shown in FIG. 36, the time division multiplexed signal is transmitted from the transmitter via the transmission path. , The optical switch 22A can output, as two separated signals, two optical signals constituting the input optical time-division multiplexed signal based on the drive signal from the drive circuit 24A.

Note that the 2 output from the optical switch 22A is
The two separated signals are output to a not-shown identification unit, and are respectively identified as separated signals. In addition, optical DEMUX2
At 0A, the operating point stabilization control circuit 29A
Operating point stabilization control basically similar to that of the above-described first embodiment is performed. That is, two clock signals for the optical time-division separation processing supplied to the optical switch 22A are added to the predetermined low-frequency signal f ₀ preset by the low-frequency oscillator 23.
Are superimposed. Further, a phase detection / bias supply circuit 28
In one example, the low-frequency signal f ₀ component of one of the two separated signals after the time-division separation processing by the optical switch 22A is divided into the optical branching unit 25, the light receiver 26, and the band-pass filter 2.
Is input through 7, is input to the low-frequency signal f ₀ from the low-frequency oscillator 23.

Subsequently, the phase detection / bias supply circuit 28
Then, the low-frequency signal f ₀ component in the optical signal after the time-division separation processing by the above-described optical switch 22A and the low-frequency oscillator 2
3 is compared with the low-frequency signal f _0, and a DC bias voltage based on the phase difference is supplied while being superimposed on a drive signal for the optical switch 22A. As a result, the clock signal supplied to the optical switch 22A is
The control is performed such that the operating point on the operating characteristic of No. 2 becomes a fixed position.

As described above, also in the third embodiment of the present invention, the operation point stabilization control can be performed in the operation point stabilization control circuit of the optical DEMUX 20A as a time division demultiplexing device. As in the case of (1), there is an advantage that a desired optical time division demultiplexing process can be performed while maintaining a sufficient light output intensity while compensating for the operating point drift for the optical time division multiplexed signal.

Further, by configuring an optical time division demultiplexer using a 1 × 2 Mach-Zehnder optical switch,
The device configuration can be simpler than the device configuration using the x1 Mach-Zehnder type optical switch, and there is an advantage that the cost for configuring the device can be reduced. (D) Description of Fourth Embodiment FIG. 9 is a block diagram showing an optical time division demultiplexer according to a fourth embodiment of the present invention. The optical time division demultiplexer 31 shown in FIG. As in the case of the embodiment, the present invention can be applied to an optical receiver that performs optical time division multiplexing / demultiplexing on an optical time division multiplexed signal from the optical transmitter 102 in the optical time division multiplexing transmission system as shown in FIG.

Here, the optical time division demultiplexing device 31 according to the fourth embodiment is the same as that in the first embodiment (FIG. 4).
The optical switch for time-division separation of the optical time-division multiplexed signal is connected in series in two stages. That is, the optical time-division separation device 3 shown in FIG.
1, for example, converts an input optical time division multiplexed signal of 4 × B gigabit / second (for example, 40 Gb / s) to B gigabit / second.
It can be separated into optical signals of seconds (for example, 10 Gb / s).

Therefore, according to the optical receiver 103 for separating the two-series optical time-division multiplexed signal shown in FIG. 32, for example, as shown in FIG. Is the optical DEMUX 122-1 to 12
By applying as 2-4, an optical receiver 120 that separates and identifies four series of optical time-division multiplexed signals can be configured.

In FIG. 10, reference numeral 121 denotes an optical branching unit that branches the received optical time division multiplexed signal into four,
123-1 to 123-4 are optical DEMUX 122-1 to
An identification unit that identifies the separated signal from 122-4. By the way, the above-mentioned optical DEMUX 122-1 to 122
As shown in FIG. 9, the optical time division demultiplexing device 31 applied as -4 includes a clock signal generation unit 21 that generates a clock signal for optical time division demultiplexing processing of a received optical signal, and has two stages connected in series. Connected optical switches 32-1 and 32-3
2-2. Here, also in each of the optical switches 32-1 and 32-2 according to the fourth embodiment, the optical signal is time-division-divided based on the clock signal from the clock signal generation unit 21, and the 1 × 1 Mach-Zehnder It is composed of a type optical switch.

Further, in the optical time division demultiplexer 31 shown in FIG. 9, each of the switches 32-1 and 32-2 has
Low frequency oscillators 33-1 and 33-2, drive circuit 34-1,
34-2, band pass filters 37-1 and 37-2, and phase detection / bias supply circuits 38-1 and 38-2, and an optical splitter 35 and a light receiver 36.

Here, each of the low-frequency oscillators 33-1 and 33-
Numeral 2 is for generating predetermined low frequency signals different from each other. For example the low frequency oscillator 33-1 intended to generate a low frequency signal f _1, the low frequency oscillator 33-2 low frequency signal f
Is what happens to ₂ . The driving circuit as a low-frequency superimposing unit 34-1, the clock signal generator to the clock signal from 21, the optical switch 32-1 by superimposing a predetermined low frequency signal f ₁ from the low frequency oscillator 33-1 Is output as a clock signal corresponding to.

Further, a driving circuit 3 as a low frequency superimposing unit
4-2 generates a clock frequency that is (１ ／) times the clock frequency of the clock signal from the clock signal generation unit 21 and adds a predetermined low-frequency signal f ₂ from the low-frequency oscillator 33-2 to the generated clock signal. Are superimposed and output as a clock signal to the optical switch 32-2. Therefore, in the optical switch 32-1, as shown in FIG. 11, the received optical time division multiplexed signal a (4 × B gigabit / second) is time-based based on the clock signal b from the drive circuit 34-1. The signal is subjected to a division and separation process, and is output as a separation signal c of 2 × B gigabit / second. Similarly to the case of the first embodiment described above, when the operating point drift occurs in the optical switch 32-1, the separation signal c so as to include the low frequency component f ₁ I have.

Similarly, the optical switch 32-2 outputs the clock signal d from the drive circuit 34-2 for the optical signal c of 2 × B gigabit / second input from the optical switch 32-1.
Is subjected to a time-division demultiplexing process and output as a B gigabit / second optical signal. In this case, when the operating point drift in the optical switch 32-2 is occurring, the separation signal e has to include the low frequency component f _2.

The above-mentioned optical switches 32-1 and 32-2
Since the low-frequency signals f ₁ and f ₂ superimposed on the clock signal for −2 have different frequencies from each other, the operating point drift in the optical switches 32-1 and 32-2 of each stage is detected. Low-frequency signal to be superposed by another optical switch can be detected separately.

In other words, the last-stage optical switch 32-2
From the delivery light from, in the difference of the frequency of the low-frequency signal superimposed (f _1, f _2), the optical switches 32-1,32
The low-frequency component appearing due to the operating point drift at -2 can be separated and detected. Further, in the above-described clock signal generation unit 21, the received optical time-division multiplexed signal is converted into a B signal by a PLL (Phase Locked Loop) or the like.
A gigahertz and 2 × B gigahertz clock signal is generated and output to the driving circuit 34-2 and the driving circuit 34-1.

The optical splitting section 35 splits the optical signal output from the optical switch 32-2 at the last stage into two, and one of the split optical signals is used as the identification section 123-1 at the subsequent stage.
, And the other optical signal is output to the light receiver 36. The photodetector 36 converts the branched optical signal from the optical branching unit 35 into an electric signal, and the converted electric signal is output to each of the band-pass filters 37-1 and 37-2. .

[0112] Further, the bandpass filter 37-1, which from the converted signal into an electrical signal for the optical signal output from the optical switch 32-2 in the last stage for detecting the low frequency signal f _1, similarly , Bandpass filter 37-2
Is obtained by converting the optical signal output from the last-stage optical switch 32-2 into a low-frequency signal f ₂ from a signal converted into an electric signal.
Is to be detected. Therefore, the band-pass filters 37-1 and 37-2 described above function as low-frequency signal detection units.

The phase detection / bias supply circuit 38-
1 is a low frequency signal f from the low frequency oscillator 33-1.₁Rank
Phase and low-frequency signal detected by bandpass filter 37-1
No. f ₁The bias voltage corresponding to the phase difference
This is applied to the switch 32-1. Similarly, the phase
The detection / bias supply circuit 38-2 includes a low-frequency oscillator 33.
-2 low frequency signal f_TwoPhase and bandpass filter 3
Low frequency signal f detected at 7-2_TwoPhase difference
Applied bias voltage to the optical switch 32-2
Is what you do.

In other words, each of the above-mentioned phase detection / bias supply circuits 38-1 and 38-2 functions as a bias voltage supply unit.
As in the embodiment (see reference numeral 28), FIG.
It has a configuration as shown in FIG. Therefore, the low-frequency oscillators 33-1, 33-2 and the driving circuits 34-1, 34- provided corresponding to the optical switches 32-1, 32-2 described above.
2. The clock signals supplied to the optical switches 32-1 and 32-2 by the band-pass filters 37-1 and 37-2 and the phase detection / bias supply circuits 38-1 and 38-2 are
An operation point stabilization control circuit for controlling the operation points on the operation characteristics of the optical switches 32-1 and 32-2 to be at a fixed position is configured.

With the above configuration, in the optical time division demultiplexing apparatus according to the fourth embodiment of the present invention, for example, a time division multiplexed signal (4 × B) in which four series of optical signals are multiplexed from a transmitter via a transmission path. Gigabit / second), the optical DEMUX
In the clock signal generator 21 of each optical time division demultiplexer 20 arranged at the position of 122-1 to 122-4, the optical switch 32 is converted from the time division multiplexed signal received by the receiver.
At -1 and 32-2, a clock signal for performing optical time division separation is generated.

In this case, the clock signal generator 21 generates a 2 × B hertz clock signal as a clock signal for performing time-division separation in the optical switch 32-1 while the optical switch 32-2. Generates a clock signal of B hertz as a clock signal for performing time division separation. Further, in the driving circuit 34-1 superposes the low frequency signal f ₁ from the low frequency oscillator 33-1 on the clock signal from the clock signal generation element 21, which in one of the electrodes in the optical switch 32-1 Supply. Similarly, also in the drive circuit 34-2, the low frequency oscillator 3 is applied to the clock signal from the clock signal generation unit 21.
It superimposes the low frequency signal f ₂ from 3-2, and supplies it to one of the electrodes in the optical switch 32-2.

Here, in the optical switch 32-1,
As shown in FIG. 11, an optical time-division multiplexed signal a (a multiplexed signal including four series of signals) as a received optical signal input via the optical branching unit 121 is used as the drive circuit 34-
Clock signal b for optical time-division separation processing generated in 1
Is output as a separated signal c.

Similarly, in the optical switch 32-2,
As shown in FIG. 11, the output signal c from the optical switch 32-1 is modulated by the clock signal d for the optical time-division separation processing generated by the above-described drive circuit 34-2, thereby forming four series. Any one of these series of separated signals e
Is output as In the optical switches 32-1 and 32-2, the low frequency signal f _1, the separation in a state affected by the amplitude modulation of f ₂ signal c described above, e is output.

That is, as in the case of the first embodiment (see (S4) of FIG. 6), the optical switch 32-1 (32-
2) The driving signal b (d) is applied to the electrodes in a state where no operating point drift due to temperature change or aging change occurs.
Is applied, the output optical signal has a frequency of 2f ₁ (2
Although the component of f ₂ ) is included, the component of f ₁ (f ₂ ) is not included.

When the drive signal b (d) is applied to the electrodes while the operating point drift occurs in the optical switch 32-1 (32-2), the output optical signal has a frequency The component of f ₁ (f ₂ ) is included. In the optical branching unit 35, the output optical signal from the optical switch 32-2 is branched, and one of the branched optical signals is separated into the identification unit 1 in the subsequent stage.
23-1 to 123-4, while the other output optical signal is converted into an electric signal by the photodetector 36 and then output to the band-pass filters 37-1 and 37-2.

In the band-pass filter 37-1, the frequency f included in the optical signal output from the optical switch 32-2 is determined based on the signal converted into the electric signal by the light receiver 36.
Detect _one component. When the frequency f ₁ component in the band-pass filter 37-1 is detected operating point drift occurs in the optical switch 32-1. That is, the phase detection and bias supply circuit 38-1, the low frequency signal f ₁ and the low-frequency oscillator 33 from the band-pass filter 37-1
Performing phase comparison between the low frequency signal f ₁ from -1. As a result, a DC bias voltage that causes the operating point on the operating characteristic curve of the optical switch 32-1 to be at a fixed position is superimposed on the clock signal from the drive circuit 34-1 on the electrode of the optical switch 32-1. Output.

[0122] Similarly, in the band-pass filter 37-2, based on the signal converted into an electric signal by the light receiving unit 36, the component of the frequency f ₂ included in the output light signal from the optical switch 32-2 To detect. Bandpass filter 37-
When the component of the frequency f2 is detected at ₂ , the operating point drift occurs in the optical switch 32-2. That is, in the phase detection / bias supply circuit 38-2,
A low frequency signal f ₂ from the band-pass filter 37-2 performs phase comparison between the low frequency signal f ₂ from the low frequency oscillator 33-2. As a result, a DC bias voltage such that the operating point on the operating characteristic curve of the optical switch 32-2 is at a fixed position is applied to the drive circuit 34-
2 and is superimposed on the clock signal from 2 and output.

Accordingly, in the optical switches 32-1 and 32-2, a DC bias voltage is applied to the clock signal as a drive signal in accordance with the detected operating point drift, and the optical switches 32-1 and 32-2 Is controlled so that the operating point on the operating characteristic of the above becomes a fixed position. As described above, according to the optical time division demultiplexer according to the fourth embodiment of the present invention, the optical switch 32-
Since the operating points on the operating characteristic curves 1 and 32-2 can be controlled to be stabilized, the desired operating point drift can be compensated for the optical time-division multiplexed signal while compensating the operating point drift as in the first embodiment. In addition to the advantage that the optical time-division separation process can be performed while maintaining a sufficient light output intensity,
In the band-pass filters 37-1 and 37-2 provided corresponding to the optical switches 32-1 and 32-2, the low-frequency signals f ₁ and f ₁ , Since f ₂ can be detected, the branching unit 35 for branching the output optical signal and the photodetector 36 for converting the branched optical signal into an electric signal can be shared, so that the number of times the optical signal is branched is reduced. By reducing the number, the loss due to optical branching can be reduced, but there is an advantage that the size of the circuit can be reduced and the cost for configuring the device can be reduced.

In the optical time division demultiplexer 31 according to the fourth embodiment, the 1 × 1 Mach-Zehnder optical switches 32-1 and 32-2 are connected in two stages in series. According to the above, more than two stages may be connected in series in multiple stages, and in this case, an optical receiver for separating an optical time division multiplexed signal in which four or more sequences of signals are multiplexed may be provided as described above. It can be configured according to the optical receiver shown in FIG.

In this case, the low-frequency oscillator provided for each optical switch is configured to generate different low-frequency signals, and the band-pass filter for each optical switch also has a low-frequency signal. It is configured to pass a low frequency signal similar to the frequency generated by the frequency oscillator. Further, in this case, the frequency of the drive clock signal input to each optical switch is, for example, the above-described PL.
It is possible to use half the frequency of the drive clock signal of the preceding optical switch, which is generated by appropriately using L or the like.

(E) Description of Fifth Embodiment FIG. 12 is a block diagram showing an optical time division demultiplexer according to a fifth embodiment of the present invention. The optical time division demultiplexer 40 shown in FIG. As in the above embodiments, the present invention is applied to an optical receiver that performs optical time division multiplexing and demultiplexing on an optical time division multiplex signal from the optical transmitter 102 in the optical time division multiplex transmission system as shown in FIG. Can be.

Here, the optical time-division demultiplexing device 40 according to the fifth embodiment differs from that of the fourth embodiment in that the optical switch is not a 1 × 1 Mach-Zehnder type, but one.
The difference is that a × 2 Mach-Zehnder type optical switch is used and that the 1 × 2 Mach-Zehnder type optical switch is connected in series in three stages, but is similar to that of the above-described fourth embodiment. A clock signal generator 21 is provided.

That is, one of the two output terminals of the optical switch 42-1 is connected to the input terminal of the optical switch 42-2, and one of the two output terminals of the optical switch 42-2 is connected to the optical switch 42-2. -3, and one of the two output terminals of the optical switch 42-3 is branched by the optical branching unit 45. Further, corresponding to each of the optical switches 42-1 to 42-3, the low-frequency oscillators 43-1 to 43-3 and the driving circuits 44-1 to 4-3 having substantially the same functions as those in the fourth embodiment described above.
44-3, band-pass filters 47-1 to 47-3, and phase detection / bias supply circuits 48-1 to 48-3 are provided, and an operating point stabilization control circuit is configured by these functional units. It has become.

[0129] The low frequency oscillator 43-1～43-3 provided for each optical switch 42-1～42-3 is configured to generate a different low-frequency signal f ₁ ~f ₃ together, The bandpass filters 47-1 to 47-3 for each of the optical switches 42-1 to 42-3 also pass low-frequency signals similar to the frequencies generated by the low-frequency oscillators 43-1 to 43-3. It is configured to

Accordingly, each of the band-pass filters 47-1 to 47-1
In 7-3, when it is detected that the components of the low frequency signal f ₁ ~f ₃ is included in the output light signal from the optical switch 42-3 in the last stage, each optical switch 42-1～42-3 Therefore, in the phase detection bias supply circuits 48-1 to 48-3, the operation points on the operation characteristic curves of the optical switches 42-1 to 42-3 are fixed positions. Such a DC bias is supplied.

With the above-described configuration, in the optical time division demultiplexer 40 according to the fifth embodiment of the present invention, the clock signal generator 21 converts the received optical time division multiplexed signal into the optical switches 42-1 to 42-3. Generates a clock signal for performing the optical time-division separation in each of the driving circuits 44-1 to 44-1.
In 44-3, predetermined low frequency signals f _{1 to} f ₃ are superimposed on the clock signal from the clock signal generator 21 and output.

In the optical switch 42-1 as shown in FIG. 13, an optical time-division multiplexed signal a (for example, 4 × B gigabit / second) as an input received optical signal is transmitted by a drive circuit 44-1. The optical time-division multiplexed signal a is separated by modulating with the generated clock signal b (for example, B gigahertz) for the optical time-division separation processing, and the separated signals c,
Output as d.

That is, the separated signal d (3 × B gigabit / second) separated based on the above-mentioned clock signal b is input from one output terminal to the optical switch 42-2, while the other separated signal c (B gigabits / second) can be identified by an identification unit (not shown) at a later stage. Similarly, in the optical switch 42-2, the optical switch 42-2
1 is input to the drive circuit 44 described above.
By modulating with the clock signal e for optical time division separation processing generated at -2, the separation signal d is further separated into separation signals f and g, and two signals are output.

In this case, the separated signal g (2 × B gigabit / second) separated based on the above-described clock signal e is input from one output terminal to the optical switch 42-3, while the other is output. The separated signal f (B gigabit / second) can be identified by a later-stage identification unit (not shown). Further, in the optical switch 42-3, the output signal g from the optical switch 42-2 is input, and modulated by the clock signal h for the optical time division separation process generated in the above-described drive circuit 44-3. Thus, the separation signal g
Is further separated into separation signals i and j, and two signals are output.

That is, the separated signal j (B gigabit / second) separated based on the above-described clock signal h is branched into two in the subsequent branching unit 45, while the remaining separated signal i (B
Gigabits / second) can be identified by an identification unit (not shown) at a later stage. Therefore, the drive signal given to the three optical switches 42-1 to 42-3 is a pulse signal having the same gate width as the time slot T of the input optical signal and a phase interval shifted by one time slot T. , The input optical signal can be extracted to separate outputs every four bits.

In the optical switch 42-3, the separated signals i and j are affected by the low frequency signals f _{1 to} f ₃ superimposed on the clock signal in the driving circuits 44-1 to 44-3. Is output. That is, the optical switch 42
In the state where no operating point drift due to temperature change or aging change occurs in all of the low frequency signal f
_When the drive signals b, e, and h on which ₁ , f ₂ , and f ₃ are superimposed are applied to the electrodes, the output optical signal has the frequencies 2f ₁ , 2f _2.
And it contains the component of 2f _3, the component of the frequency f _1, f ₂ or f ₃ is not included.

When drive signals b, e, and h are applied to the electrodes in a state where an operating point drift occurs in any of the optical switches 42-1 to 42-3, the output optical signal Contains any one of the frequencies f ₁ , f ₂ , and f ₃ . In the optical branching unit 45, the output optical signal from the last-stage optical switch 42-3 is branched, and the branched output optical signal is converted into an electric signal by the optical receiver 46.

In the band-pass filter 47-1, the frequency f included in the output optical signal from the optical switch 42-3 is determined based on the signal converted into the electric signal by the light receiver 46.
Detect _one component. When the frequency f ₁ component in the band-pass filter 47-1 is detected operating point drift occurs in the optical switch 42-1. In this case, the phase detection and bias supply circuit 48-1, was subjected to phase comparison between the low frequency signal f ₁ from the band-pass filter 47-1 and the low frequency signal f ₁ from the low frequency oscillator 44-1 Based on the result, a DC bias voltage such that the operating point on the operating characteristic curve of the optical switch 42-1 is at a fixed position is applied to the drive circuit 44-
1 is superimposed on the clock signal from 1 and output.

[0139] Similarly, in the band-pass filter 47-2, based on the converted signal into an electrical signal by the light receiving unit 46, detecting the frequency f ₂ component contained in the output light signal from the optical switch 42-2 I do. Bandpass filter 47-2
Optical switch 4 when the frequency f ₂ component is detected by
In 2-2, an operating point drift has occurred. That is,
The phase detection and bias supply circuit 48-2, on the basis of the result of the phase comparison between the low frequency signal f ₂ from the band-pass filter 47-2 and the low frequency signal f ₂ from the low frequency oscillator 44-2, light A DC bias voltage that causes the operating point on the operating characteristic curve of the switch 42-2 to be at a fixed position is superimposed on the clock signal from the drive circuit 44-2 and output to the electrode of the optical switch 42-2.

[0140] Further, in the bandpass filter 47-3, based on the converted signal into an electrical signal by the light receiving unit 46 detects the frequency f ₃ component contained in the output light signal from the optical switch 42-3 . Bandpass filter 47-3
Optical switch 4 when the frequency f ₃ component was found in the
An operating point drift occurs in 2-3. That is,
The phase detection and bias supply circuit 48-3, on the basis of the result of phase comparison between the low frequency signal f ₃ from the band-pass filter 47-3 and the low frequency signal f ₃ from the low frequency oscillator 44-3, an optical switch A DC bias voltage such that the operating point on the operating characteristic curve of the optical switch 42-3 is at a fixed position is superimposed on the clock signal from the drive circuit 44-3 and output to the electrode of the optical switch 42-3.

Thus, the optical switches 42-1 to 42-
In (3), a DC bias voltage is applied to the clock signal as a drive signal in accordance with the detected operating point drift, so that the operating points on the operating characteristics of the optical switches 42-1 to 42-3 are fixed. Is controlled. in this way,
Also in the fifth embodiment of the present invention, the optical switch 42-1
42-3 can be controlled so as to stabilize the operating point on the operating characteristic curve, so that the desired operating point drift can be compensated for the optical time division multiplexed signal while compensating the operating point drift as in the case of the first embodiment. There is an advantage that the optical time division separation process can be performed while maintaining a sufficient light output intensity.

Further, a branching unit 45 for branching the output optical signal
And a light receiver 46 for converting the branched optical signal into an electric signal
Can be shared as components for compensating the operating point drift of each of the optical switches 42-1 to 42-3, so that the circuit can be downsized and the cost for configuring the device can be reduced. There are also benefits that can be done.

Incidentally, also in the fifth embodiment of the present invention,
As in the case of the above-described fourth embodiment, 1
The number of stages of the × 2 Mach-Zehnder optical switch can be arbitrarily set. (F) Description of Sixth Embodiment FIG. 14 shows an optical time-division splitting device according to a sixth embodiment of the present invention. The optical time-division splitting device 50 shown in FIG. Similarly to FIG.
Optical transmitter 1 in an optical time division multiplex transmission system such as 2
The present invention can be applied to an optical receiver that performs optical time division multiplexing and demultiplexing on the optical time division multiplexed signal from the optical receiver 02.

Here, the optical time division demultiplexing device 50 according to the sixth embodiment includes the same clock signal generation unit 21 as that of the fifth embodiment (see reference numeral 40), and 1 × as an optical switch. Although a two-Mach-Zehnder optical switch is used, the difference is that optical switches 52-2 and 52-3 for separating the two separated signals output from the first-stage optical switch 52-1 are provided.

That is, in the optical time division demultiplexer 50 shown in FIG. 14, one of the two output terminals of the optical switch 52-1 is connected to the input terminal of the optical switch 52-2, while The other of the two output terminals of 52-1 is connected to the input terminal of the optical switch 52-3. Also, in the optical time-division demultiplexing device 50 according to the sixth embodiment, the low-frequency oscillator 53 basically similar to that in the above-described fifth embodiment corresponds to each of the optical switches 52-1 to 52-3. -1 to 53-3, drive circuits 54-1 to 54-
3. The bandpass filters 57-1 to 57-3 and the phase detection / bias supply circuits 58-1 to 58-3 are provided.

That is, in each of the driving circuits 54-1 to 54-3, the desired low frequency signals f ₁ and f ₁ from the low frequency oscillators 53-1 to 53-3 are added to the clock signal from the clock signal generator 21. By superimposing ₂ , ₂ is output as a drive signal for each of the optical switches 52-1 to 52-3. Here, the frequency f ₁ of the low-frequency signal superimposed on the clock signal to the first-stage optical switch 52-1 is:
And the frequency f ₂ of the low-frequency signal superimposed on the subsequent stage of the clock signal to the optical switch 52-2 and 52-3 are set to be different from each other, thereby, the optical switch 52-1 in each stage 52-3, the low-frequency signal for detecting the operating point drift can be detected separately from the low-frequency signal superimposed by another optical switch.

One of the two output terminals of the optical switch 52-2 has the same branching unit 55-1 and light receiver as those in the fifth embodiment (see reference numerals 45 and 46). 56-1. That is, the branching unit 55-1 and the light receiver 56-1 are connected to each optical switch 52-
1, 52-2 are shared as components for compensating the operating point drift.

[0148] That is, in the band-pass filter 57-1 detects a low frequency signal f ₁ component contained in the separated signal from the optical switch 52-2 which is converted into an electric signal by the optical receiver 56-1 in the band-pass filter 57-2, and detects the components of the low frequency signal f ₂ included in the separated signal from the optical switch 52-2.

Thus, in the phase detection / bias supply circuits 58-1 and 58-2, the band-pass filter 57
Based on the detection information of the low frequency signals f ₁ and f ₂ from −1 and 57-2, it is possible to supply a DC bias voltage for compensating the operating point drift in each of the optical switches 52-1 and 52-2. You can. Further, the optical switch 52
In the optical path of one of the two output terminals of the optical switch 52-3, an optical branching unit 55-2 and an optical receiver 56-2 that constitute an independent feedback system for compensating the operating point drift in the optical switch 52-3 are provided. I have it.

That is, the band-pass filter 57-3 is connected to the optical switch 52-converted to an electric signal by the optical receiver 56-2.
While detecting the component of the low frequency signal f ₂ included in the separated signals from the 3, the phase detection and bias supply circuit 58-3, the low frequency signal f from the band-pass filter 57-3
The DC bias voltage for compensating the operating point drift in the optical switch 52-3 is supplied based on the detection information of ( ₂ ).

With the above-described configuration, the optical time-division splitting device 50 according to the sixth embodiment of the present invention also provides
In the same manner as in the embodiment, the clock signal generation unit 21 converts the received optical time division multiplexed signal into an optical switch 52.
-1 to 52-3 generate a clock signal for performing the optical time division separation, and each of the driving circuits 54-1 to 54-3.
In 54-3, superimposed and outputs a predetermined low frequency signals f _1, f ₂ to the clock signal from the clock signal generation section 21.

In the optical switch 52-1, an optical time division multiplexed signal (for example, 4 × B
Clock signal b (for example, 2 gigabits / second) for optical time-division separation processing generated by the drive circuit 54-1.
.Times.B gigahertz) to separate the optical time-division multiplexed signal and output it as two separated signals (for example, 2.times.B gigabit / second).

The separated signal output from one output terminal of the optical switch 52-1 is input to the optical switch 52-2, and the optical switch 52-2 further outputs two separated signals (for example, B gigabit / second). ) And output. Similarly, the separated signal output from the other output terminal of the optical switch 52-1 is input to the optical switch 52-3,
The optical switch 52-3 further separates and outputs two separated signals (for example, B gigabit / second).

In the optical branching section 55-1, the output optical signal from the last-stage optical switch 52-2 is branched, and the branched output optical signal is converted into an electric signal by the optical receiver 56-1. You. In the optical branching unit 55-2,
The output optical signal from the optical switch 52-3 is branched,
The branched output optical signal is converted into an electric signal by the light receiver 56-2.

By the way, the optical switches 52-2 and 52-3
In, the separated signals are output in a state affected by the low frequency signals f ₁ and f ₂ superimposed on the clock signal in the drive circuits 54-1 to 54-3. That is, in the optical switch 52-2, the optical switches 52-1 and 52-2 are used.
In any of the above, when the driving signal on which the low frequency signals f ₁ and f ₂ are superimposed is applied to the electrodes in a state where the operating point drift due to the temperature change and the aging change does not occur, the output optical signal Contains components of frequencies 2f ₁ and 2f ₂ ,
Component of the frequency f ₁ or f ₂ is not included.

The optical switches 52-1 and 52-2 are not provided.
If the operating point drifts in
Wave signal f₁, F_TwoIs applied to the electrodes.
Then, the output optical signal has a frequency f₁, F_TwoHorse
This means that one of the components is contained. Band communication
In the over-filter 57-1, the electric power is
Based on the signal converted to the air signal, the optical switch 52-
Frequency f included in the output optical signal from ₁Detect components
You.

Here, when an operating point drift occurs in the optical switch 52-1, the band-pass filter 57-
Low frequency signal f ₁ detected by the first and low-frequency oscillator 54-
Based on the phase difference from the low-frequency signal f1 from 1 to ₁ , a DC bias voltage such that the operating point on the operating characteristic curve of the optical switch 52-1 is at a fixed position is applied to the electrode of the optical switch 52-1. The output is superimposed on the clock signal from the drive circuit 54-1.

Similarly, in the band-pass filter 57-2, the frequency f ₂ component included in the optical signal output from the optical switch 42-2 based on the signal converted into the electric signal by the optical receiver 56-1. Is detected. Here, the optical switch 5
When the operating point drift occurs in 2-2, the low frequency signal f ₂ detected by the band-pass filter 57-2 in the phase detection / bias supply circuit 58-2.
A low frequency oscillator 54-2 phase comparison result between the low frequency signal f ₂ from based on (phase difference), the operating characteristics operating point on the curve becomes constant position such DC bias voltage of the optical switch 52-2 Is superimposed on the clock signal from the drive circuit 54-2 and output to the electrode of the optical switch 52-2.

[0159] Further, in the bandpass filter 57-3, based on the converted signal into an electric signal by the optical receiver 56-2, the frequency f ₂ component contained in the output light signal from the optical switch 52-3 To detect. Here, the optical switch 4
When the operating point drift occurs in the 2-3 phase comparison between the low frequency signal f ₂ detected by the band-pass filter 57-3 and the low frequency signal f ₂ from the low frequency oscillator 54-3 Based on the result, a DC bias voltage such that the operating point on the operating characteristic curve of the optical switch 52-3 is at a fixed position is applied to the electrode of the optical switch 52-3 in the clock signal from the drive circuit 54-3. The output is superimposed.

Thus, the optical switches 52-1 to 52-
In 3, in accordance with the detected operating point drift, a DC bias voltage is applied to the clock signal as a driving signal, and the operating points on the operating characteristics of the optical switches 52-1 to 52-3 become fixed positions. Is controlled as follows. As described above, also in the optical time division demultiplexing apparatus according to the sixth embodiment of the present invention, it is possible to control so as to stabilize the operating points on the operating characteristic curves of the optical switches 52-1 to 52-3. As in the first embodiment, there is an advantage that a desired optical time division demultiplexing process can be performed while maintaining a sufficient optical output intensity while compensating for an operating point drift for the optical time division multiplexed signal.

Further, a branching unit 55 for branching the output optical signal
-1 and the photodetector 56-1 for converting the branched optical signal into an electric signal can be shared as a component for compensating the operating point drift of each of the optical switches 52-1 and 52-2. Also, there is an advantage that the number of times of branching of the circuit can be reduced, which can contribute to downsizing of the circuit and cost reduction for configuring the device.

Note that in the sixth embodiment of the present invention,
As in the above-described fourth and fifth embodiments, the number of stages of 1 × 2 Mach-Zehnder optical switches connected in series can be arbitrarily set. (G) Description of Seventh Embodiment FIG. 15 is a block diagram showing an optical time division demultiplexer according to a seventh embodiment of the present invention. The optical time division demultiplexer 60 shown in FIG. As in the case of the embodiment, the present invention can be applied to an optical receiver that performs optical time division multiplexing / demultiplexing on an optical time division multiplexed signal from the optical transmitter 102 in the optical time division multiplexing transmission system as shown in FIG.

Here, the optical time-division splitting device 60 according to the seventh embodiment has the same configuration as that of the fifth embodiment described above.
1 × 2 Mach-Zehnder type optical switches 62-1 to 62
-3 are connected in series in three stages, except that the compensation control of the operating point drift in each of the optical switches 62-1 to 62-3 is performed by switching over time. different.

Further, in the optical time division demultiplexing device 60 shown in FIG. 15, the same clock signal generation unit as that of the fifth embodiment (reference numerals 21, 44-1 to 44-3, 45, 46) is used. 21, drive circuits 64-1 to 64-
3, a light branching section 65 and a light receiver 66 are provided, and detailed description thereof is omitted. A low-frequency oscillator 63 generates a predetermined low-frequency signal f _0.
7 is a band-pass filter as a low frequency signal detection element for detecting the low frequency signal f ₀ from the optical signal output from the optical switch 62-3 in the last stage.

Reference numeral 68A denotes a phase detection circuit serving as a phase difference detection unit. The phase detection circuit 68A detects the phase of the low-frequency signal f ₀ from the low-frequency oscillator 63 and the low-frequency signal detected by the band-pass filter 67. It detects a difference from the phase of the frequency signal f ₀ , and can be constituted by, for example, the inverting / full-wave rectifying unit 28 a shown in FIG. Also, 6
1-1 is a first changeover switch, the first changeover switch 61-1 based on the switching control of the oscillator circuit 70 for generating a timing pulse of the period 1 / F _0, the low from the low frequency oscillator 63 The frequency signal f ₀ is supplied to the driving circuit 64 of each stage.
-1 to 64-3 and selectively output.

[0166] Further, 61-2 denotes a second changeover switch, this for the second changeover switch 61-2, based on the switching control by the timing pulse of the period 1 / F ₀ from the oscillation circuit 70, phase detection and Bias voltage supply circuit 6
8A from the optical switches 62-1 to 62-2.
-3 for selectively switching and outputting the bias voltage for operating point compensation.

Reference numerals 68B-1 to 68B-3 denote bias holding circuits serving as bias voltage holding units. These bias holding circuits 68B-1 to 68B-3 are provided with optical switches 62-1 to 62- at each stage. 3 for each phase detection
The bias voltage information from the bias voltage supply circuit 68A is temporarily stored therein. More specifically, as shown in FIG. 16, an integrating circuit 69a and a voltage follower 69b are provided.
It is configured with.

In this case, the integrating circuit 69a constituting each of the bias voltage holding sections 68B-1 to 68B-3.
Has a function as the low-pass filter 28b shown in FIG. 5 described above, and performs a low-pass filter process from the phase comparison result information from the phase detection / bias supply circuit 68A to extract a DC component. I have. Here, the integrating circuit 69a shown in FIG. 16 includes an OP amplifier 69a-1, a capacitor 69a-2, a resistor 69a-3,
69a-4 and OP amplifier 69a-
1, switches 69a-5 to 69a- for controlling ON / OFF of a conduction state of a capacitor 69a-2 and a resistor 69a-3.
7 is provided.

Each of the switches 69a-5 to 69a-7
Is a switching signal C from the oscillation circuit 70. ₁~ C_ThreeOn the basis of
ON / OFF control is performed in synchronization with each other.
In particular, these switches 69a-5 to 69a-7
In the ON state, the phase difference from the phase detection circuit 68A
Output DC bias voltage based on detection information
If the switch is off,
The charge when it is turned off to the capacitor 69a-2.
Can be stored. Thereby, the switch OF
The voltage immediately before F can be output as a DC bias voltage
It has become so.

In other words, the bias holding circuit 68B-1
In the case where the ~68B-3 switching signals C ₁ -C ₃ above not input, a bias holding circuits 68B-1 to 68
B-3 is in a state capable of outputting the DC bias voltage information held, when the switching signal C ₁ -C ₃ is inputted, is held by the bias voltage holding circuit 68B-1~68B-3 The bias voltage information is updated to the bias voltage information from the phase detection / bias supply circuit 68A.

The voltage follower 69b is connected to the output terminal of the integrating circuit 69a and each of the optical switches 68B-1 to 68B.
-3 so as to prevent a current from flowing therethrough, and includes a resistor 69b-1 and an OP amplifier 69b-2. Further, while the above-described oscillation circuit 70 is configured by, for example, a multivibrator and an analog switch, the timing pulse supplied to the first switch 61-1 and the second switch 61-2 at a period of 1 / F ₀ and each the switching signal C ₁ -C ₃ outputted to the bias holding circuits 68B-1~68B-3, both adapted to synchronously output.

The switching period 1 / F ₀ of the operating point stabilization control generated by the oscillation circuit 70 is set as short as possible within a range sufficiently longer than the time constant of the control. In other words, by the timing pulse from the oscillator 70,
The first switch 61-1 is controlled so that the low-frequency oscillator 63 and the drive circuit 64-1 conduct, and the phase detection circuit 68
When the second switch 61-2 is controlled so that A and the bias holding circuits 68B-1 to conduct, the switching signal C _1, the bias holding circuits 68B-1 of the switch 69a-5~69a-7 oF Although There has been set to be oN, this time, by the switching signals C _2, C _3, switches 69a-5~69a-7 of the corresponding integration circuits 69a
F.

As a result, the three driving circuits 64-1 to 64-6
4-3, any one of the driving circuits 64-k (k; 1,
2 or 3) from the low frequency oscillator 63
Low frequency signal f₀Are superimposed, while the phase circuit 68A
Bias holding circuit 68B-k by the DC bias voltage of
The information stored in is updated. Paraphrase
Then, the plurality of optical switches 62-1 to 62-3 described above
Generation of DC bias voltage for operating point compensation
1 / F between optical switches 62-1 to 62-3 ₀Time interval
Can be switched in order with
You.

As components of a feedback system for performing operating point compensation in each of the optical switches 62-1 to 62-3, an optical branching unit 65, a light receiver 66, a bandpass filter 67, a phase detection circuit 68A, Frequency oscillator 63
Can be shared. With the above-described configuration, the optical time division demultiplexing device 60 according to the seventh embodiment of the present invention performs reception based on the clock signal generated by the clock signal generation unit 21 as in the case of the fifth embodiment. The optical time division multiplexed signal is
-1 to 62-3 are output separately.

The oscillation circuit 70 outputs timing pulses synchronized with each other to the first changeover switch 61-1 and the second changeover switch 61-2, and any of the bias holding circuits 68B-1 to 68B-. The switching signals C _{1 to} C ₃ are output to the optical switches 62-1 to 62-3 to generate a DC bias voltage for performing the operation point compensation of the plurality of optical switches 62-1 to 62-3. 1
６２62-3 are sequentially switched at time intervals of 1 / F ₀ .

As described above, according to the optical time division demultiplexing apparatus according to the seventh embodiment of the present invention, the plurality of optical switches 62-
In order to temporally switch the operating point of the clock signal supplied to any one of the optical switches 62-1 to 62-3 to the operating characteristic of the optical switches 62-1 to 62-3, the above operation is performed. Control of the first changeover switch 61-1 and the second changeover switch 61-2, and updating of the bias voltage information held in the bias holding circuits 68B-1 to 68B-3 is controlled. In each of the optical switches 62-1 to 62-3, the components of the feedback system for performing the operating point compensation can be shared, and the number of light branches can be reduced, so that the circuit size can be reduced. There are advantages that can be.

(H) Description of Eighth Embodiment FIG. 17 is a block diagram showing an optical time division demultiplexer according to an eighth embodiment of the present invention. The optical time division demultiplexer 80 shown in FIG. As in the above embodiments, the present invention is applied to an optical receiver that performs optical time division multiplexing and demultiplexing on an optical time division multiplex signal from the optical transmitter 102 in the optical time division multiplex transmission system as shown in FIG. Can be.

Here, the optical time division demultiplexing device 80 according to the eighth embodiment is different from the above embodiments in that the input optical time division multiplexed signal is wavelength multiplexed. The difference is that a time-division separation process is performed after the wavelength separation, and the operating point stabilization control is basically the same. Therefore, the optical time division demultiplexing device 80 according to the eighth embodiment includes, as shown in FIG.
-2, wavelength separation unit 71, optical switches 72-1, 72-
2, low frequency oscillators 73-1, 73-2, driving circuit 74-
1, 74-2, an optical splitter 75, a light receiver 76, band-pass filters 77-1, 77-2, phase detection / bias supply circuits 78-1, 78-2, and an optical multiplexing unit 79. I have.

Here, the wavelength demultiplexing section 71 performs wavelength demultiplexing processing on the input received optical signal (wavelength-division multiplexed optical time-division multiplexed signal). Signal), and has a function as a first light separation unit. Also,
Each of the clock signal generators 21-1 and 21-2 performs a time-division separation process in the subsequent optical switches 72-1 and 72-2 based on the respective optical signals separated into two wavelengths by the wavelength separator 71. To generate a clock signal for performing the following.

Further, each of the low frequency oscillators 73-1 and 73-
Numeral 2 is for generating predetermined low frequency signals different from each other. For example the low frequency oscillator 73-1 intended to generate a low frequency signal f _1, the low frequency oscillator 73-2 low frequency signal f
Is what happens to ₂ . The driving circuit as a low-frequency superimposing unit 74-1, the clock signal from the clock signal generator 21-1, the optical switch 72 by superimposing a predetermined low frequency signal f ₁ from the low frequency oscillator 73-1 It is output as a clock signal for -1.

Further, the driving circuit 7 as a low frequency superimposing section
4-2, the clock signal from the clock signal generator 21-2, in which superimposes the predetermined low frequency signal f ₂ from the low frequency oscillator 73-2 to output as the clock signal for the optical switch 72-2 is there. Therefore, the optical switch 72
In the case of -1, the one optical time division multiplexed signal wavelength-separated by the wavelength separation unit 71 is subjected to time division separation processing based on the clock signal from the drive circuit 74-1 and is output as a separation signal. is there. Similarly to the case of the first embodiment described above, when the operating point drift in the optical switch 72-1 is occurring, the separation signal is adapted to contain a low frequency component f ₁ .

Similarly, the optical switch 72-2 performs time division demultiplexing processing on the other optical time division multiplexed signal demultiplexed by the wavelength demultiplexing unit 71 based on the clock signal from the drive circuit 74-2. , Are output as separated signals. In this case, when the operating point drift in the optical switch 72-2 is occurring, the separation signal has to include the low frequency component f _2.

Further, the optical multiplexing section 79 includes the optical switch 72.
The optical splitter 75 splits the optical signal output from the optical multiplexer 79 into two optical signals. Also, the light receiver 76
Is for converting the branched optical signal from the optical branching unit 75 into an electric signal, and the converted electric signal is output to each band-pass filter 77-1 and 77-2.

[0184] Further, the bandpass filter 77-1 is for the signal converted into an electrical signal for the optical signal output from the optical multiplexing section 79 for detecting the low frequency signal f _1, similarly, band-pass filter 77-2 is an optical multiplexing unit 7
For the optical signal output from the signal converted into the electric signal from the 9 detects a low-frequency signal f _2. Therefore, the band-pass filters 77-1 and 77-2 described above function as low-frequency signal detection units.

The optical switches 72-1 and 72-2 described above are used.
Since the low-frequency signals f ₁ and f ₂ superimposed on the clock signal for −2 have different frequencies from each other, the operating point drift in the optical switches 72-1 and 72-2 at each stage is detected. Low-frequency signals can be collectively detected by using only the multiplexed optical signals and distinguishing them from low-frequency signals superimposed by another optical switch.

The phase detection / bias supply circuit 78-
1 is a low frequency signal f from the low frequency oscillator 73-1.₁Rank
Phase and low-frequency signal detected by band-pass filter 77-1
No. f ₁The bias voltage corresponding to the phase difference
This is applied to the switch 72-1. Similarly, the phase
The detection / bias supply circuit 78-2 includes a low-frequency oscillator 73.
-2 low frequency signal f_TwoPhase and bandpass filter 7
Low frequency signal f detected at 7-2_TwoPhase difference
Applied bias voltage to the optical switch 72-2
Is what you do.

In other words, each of the above-described phase detection / bias supply circuits 78-1 and 78-2 functions as a bias voltage supply unit.
As in the embodiment (see reference numeral 28), FIG.
It has a configuration as shown in FIG. Therefore, the low-frequency oscillators 73-1 and 73-2 and the driving circuits 74-1 and 74- provided for the optical switches 72-1 and 72-2 described above.
2. For optical time division separation processing supplied to each of the optical switches 72-1 and 72-2 by the band-pass filters 77-1 and 77-2 and the phase detection / bias supply circuits 78-1 and 78-2. A predetermined low-frequency signal set in advance is superimposed on the clock signal of
A low-frequency signal component f _1, f ₂ in the optical signals after division demultiplexing processing time by 1,72-2, low frequency oscillator 73-1,
Based on the phase difference between the low frequency signal f _1, f ₂ components from 73-2, the clock signal supplied to the optical switches 72-1 and 72-2, the optical switches 72-1,72- 2
An operation point stabilization control circuit for controlling the operation point on the operation characteristic to be a fixed position is constituted.

With the above configuration, in the optical time division demultiplexing apparatus according to the eighth embodiment of the present invention, the wavelength demultiplexing unit 71 converts the input received optical signal (wavelength multiplexed optical time division multiplexed signal) into a wavelength. A separation process is performed. In each of the optical switches 72-1 and 72-2, the wavelength separation unit 71
For the optical time division multiplexed signal separated into two wavelengths by
Based on the respective clock signals generated by the clock signal generators 21-1 and 21-2, the same optical time-division separation processing as in the above-described embodiments is performed. After being multiplexed, the band-pass filter 77-
1, 77-2.

[0189] In the band-pass filter 77-1 detects a frequency f ₁ component contained in the output light signal from the light receiver 76. Operating point drift has occurred in the case where the frequency f ₁ component is detected by the band-pass filter 77-1, the phase detection and bias supply circuit 78-1,
By performing phase comparison between the low frequency signal f ₁ from the low frequency signal f ₁ and the low frequency oscillator 73-1 from the band pass filter 77-1 detects the operating point drift.

Further, a phase detection / bias supply circuit 78
−1, the DC based on the amount of this operating point drift
By generating a bias voltage, the optical switch 72-1 is
The output is superimposed on the clock signal from the drive circuit 74-1.
You. Similarly, the band-pass filter 77-2 receives
Frequency f included in the optical signal output from optical device 76_TwoIngredients
To detect. The frequency f is obtained by the band-pass filter 77-2. _TwoSuccess
If a minute is detected, operating point drift has occurred.
In the phase detection / bias supply circuit 78-2,
Low frequency signal f from band pass filter 77-2 _TwoAnd low lap
Low frequency signal f from wave oscillator 73-2_TwoPhase comparison
By doing so, the operating point drift is detected.

Further, a phase detection / bias supply circuit 78
-2, a DC bias voltage based on the amount of the operating point drift is generated, and the optical switch 72-2 is
The output is superimposed on the clock signal from the drive circuit 74-2. As a result, in each of the optical switches 72-1 and 72-2, a DC bias voltage is applied to the clock signal as a drive signal in accordance with the detected operating point drift.
The optical switches 72-1 and 72-2 are controlled such that the operating point on the operating characteristics is at a fixed position.

As described above, according to the optical time division demultiplexer according to the eighth embodiment of the present invention, the clock signal generator 21
-1, 21-2, wavelength separation unit 71, optical switch 72-
1 and 72-2 and an optical multiplexing unit 79, and a clock signal for optical time division demultiplexing supplied to each of the optical switches 72-1 and 72-2 is set to a predetermined different one from another. The low-frequency signals f ₁ and f ₂ are superimposed, the low-frequency signal components f ₁ and f ₂ in the optical signal after the time-division separation processing by the optical switches 72-1 and 72-2, and the low-frequency oscillator 73-1 , the low frequency signal from 73-2 f _1, f ₂
Each of the optical switches 72-1 and 72-1,
The clock signal supplied to the optical switch 72-2 is
Since it is possible to control the operating points on the operating characteristics of 2-1 and 72-2 to be at a fixed position, the light for which the optical time division demultiplexing process is performed on the optical time division multiplexed signal subjected to the wavelength multiplexing process is also performed. In addition to being able to configure a time division separator,
In each of the optical switches 72-1 and 72-2, components of a feedback system for performing operating point compensation can be shared, and the number of times of light branching can be reduced. There is an advantage that the cost for the configuration can be reduced.

In the above-described eighth embodiment, each
Operating point drift in optical switches 72-1 and 72-2
Of the low-frequency signal to be superimposed
F ₁, F_TwoIs realized by using
However, as in the case of the above-described seventh embodiment,
Low frequency signals to be folded₀While using
It is also possible to perform the switching.

In this case, the optical time division demultiplexing device 80 'shown in FIG. 18 has the same light demultiplexing unit 71 and optical switch 72 as the optical time division demultiplexing device 80 shown in FIG.
-1, 72-2, an optical multiplexing section 79, an optical branching section 75, and a light receiver 76, and those in the above-described seventh embodiment (reference numerals 61-1, 61-2, 68A, 68B-1 to 61-1).
68B-3, 70).
Changeover switch 81-1, second changeover switch 81-2, phase detection circuit 78A, bias holding circuits 78B-1, 78
B-2 and the oscillation circuit 28 are provided.

Thus, in the oscillation circuit 82, the first switching
For the switch 81-1 and the second changeover switch 81-2
Output timing pulses synchronized with each other,
Either of the bias holding circuits 78B-1 and 78B-2
Switching signal C₁₁~ C₁₂By outputting
Operating point compensation of the optical switches 72-1 and 72-2.
Generation of a DC bias voltage for each optical switch 72-1
1 / F between ~ 72-2 ₀At the time intervals of
Can be.

Therefore, according to the optical time division demultiplexer 80 'shown in FIG. 18, the components of the feedback system for performing the operating point compensation can be shared in each of the optical switches 72-1 to 72-2. Since the number of times of light branching can be reduced, there is an advantage that the size of the circuit can be reduced. (I) Description of Ninth Embodiment FIG. 19 is a block diagram showing an optical time division demultiplexer according to a ninth embodiment of the present invention. The optical time division demultiplexer 90 shown in FIG. As in the case of the embodiment, the present invention can be applied to an optical receiver that performs optical time division multiplexing / demultiplexing on an optical time division multiplexed signal from the optical transmitter 102 in the optical time division multiplexing transmission system as shown in FIG.

Here, the optical time division demultiplexing apparatus 90 according to the ninth embodiment is different from the above-described embodiments in that the time division demultiplexing is performed after the input optical time division multiplexed signal is subjected to the polarization separation processing. The difference lies in that it is configured as a polarization-independent optical time-division demultiplexing device that performs the demultiplexing process, and the mode of operating point stabilization control is basically the same. For this reason, the optical time-division separation device 90 according to the ninth embodiment
As shown in FIG. 19, the clock signal generator 21-
1, 21-2, polarization separation section 91, optical switch 92-1,
92-2, low frequency oscillators 93-1 and 93-2, drive circuits 94-1 and 94-2, optical branching unit 95, light receiver 96-1,
96-2, band-pass filters 97-1 and 97-2, phase detection / bias supply circuits 98-1 and 98-2, an optical multiplexing unit 99, and a polarization separation element 83.

Here, the polarization separation section 91 separates two polarization components (TE wave and TM wave) from the input received optical signal (wavelength multiplexed optical time division multiplexed signal). It has a function as one light separation unit. Further, each of the clock signal generators 21-1 and 21-2 is the same as that of the eighth embodiment.
As in the embodiment, the polarization separation unit 91
A clock signal for performing time-division separation processing in the optical switches 92-1 and 92-2 at the subsequent stage is generated based on the respective optical signals separated into polarized waves. , 93-2 are all those for generating a predetermined low frequency signal f _0.

Further, a driving circuit 9 as a low frequency superimposing section
4-1, the clock signal from the clock signal generator 21-1, in which superimposes the predetermined low frequency signal f ₀ from the low frequency oscillator 93-1 to output as the clock signal for the optical switch 92-1 is there. Further, the driving circuit 94-2 as a low frequency superimposing unit includes a clock signal generating unit 21-.
The clock signal from 2, in which superimposes the predetermined low frequency signal f ₀ from the low frequency oscillator 93-2 to output as the clock signal for the optical switch 92-2.

Therefore, in the optical switch (1 × 1 Mach-Zehnder type optical switch) 92-1, the polarization separation section 91
The one optical time division multiplexed signal (for example, T
(E wave) is subjected to time-division separation processing based on a clock signal from the drive circuit 94-1 and is output as a separation signal. As in the case of the above-described first embodiment, when an operating point drift occurs in the optical switch 92-1, the separated signal includes the low frequency component f ₀ . .

Similarly, the optical switch (1 × 1 Mach-Zehnder type optical switch) 92-2 drives the other optical time-division multiplexed signal (for example, TM wave) which has been polarization-separated by the polarization separation unit 91, into a drive circuit. A time-division separation process is performed based on the clock signal from 94-2, and the separated signal is output. In this case, when the operating point drift in the optical switch 92-2 is occurring, the separation signal has to include the low-frequency component f _0.

Further, the optical multiplexing unit 99 includes a polarization separation unit 91.
The optical splitter 95 multiplexes the optical signals that are polarization-separated by the optical switches 92-1 and 92-2 and are time-division-demultiplexed by the optical switches 92-1 and 92-2. Is branched into two. The polarization splitter 83 is inserted between the optical splitter 95 and the bandpass filters 97-1 and 97-2, and the split signal from the optical splitter 95 is re-polarized (TE wave, TM wave). ), And has a function as a second light separation unit that separates two polarization components in the optical signal multiplexed by the optical multiplexing unit 99.

In other words, if the polarization splitting section 91, the optical multiplexing section 99 and the polarization splitting element 83 are used, a polarization-independent optical DEMUX can be formed. Even if the low-frequency signal superimposed on the clock signal to 92-2 has the same frequency f ₀ , the low-frequency signal for detecting the operating point drift in the optical switches 92-1 and 92-2 at each stage is used. Using only the multiplexed optical signal, the signal can be collectively detected by distinguishing it from the low-frequency signal superimposed by another optical switch.

The light receiver 96-1 is provided with the polarization splitting element 8.
3 receives the TE wave that has been polarization-separated, converts the TE wave into an electric signal, and outputs the electric signal to the band-pass filter 97-1. The received TM wave is converted into an electric signal and output to the band-pass filter 97-2. Further, the band-pass filter 97-1 detects the low-frequency signal f ₀ from the signal subjected to the polarization separation and photoelectric conversion processing by the polarization separation element 83 and the light receiver 96-1. Reference numeral 97-2 denotes a polarization separation element 83 and a light receiver 96-2.
Detects the low-frequency signal f ₀ from the signal subjected to the polarization separation and photoelectric conversion processing. Therefore, the band-pass filters 97-1 and 97-2 described above function as low-frequency signal detection units.

The phase detection / bias supply circuit 98-
1 is a low frequency signal f from the low frequency oscillator 93-1.₀Rank
Phase and low-frequency signal detected by band-pass filter 97-1
No. f ₀The bias voltage corresponding to the phase difference
This is applied to the switch 92-1. Similarly, the phase
The detection / bias supply circuit 98-2 includes a low-frequency oscillator 93
-2 low frequency signal f₀Phase and bandpass filter 9
Low frequency signal f detected at 7-2₀Phase difference
Bias voltage applied to the optical switch 92-2
Is what you do.

In other words, each of the above-described phase detection / bias supply circuits 98-1 and 98-2 functions as a bias voltage supply unit.
As in the embodiment (see reference numeral 28), FIG.
It has a configuration as shown in FIG. Accordingly, the low-frequency oscillators 93-1 and 93-2 and the driving circuits 94-1 and 94- provided corresponding to the optical switches 92-1 and 92-2 described above.
2. For optical time-division separation processing supplied to each of the optical switches 92-1 and 92-2 by the band-pass filters 97-1 and 97-2 and the phase detection / bias supply circuits 98-1 and 98-2. Is superimposed on a predetermined low-frequency signal f ₀ on the clock signal of
2-1 and 92-2, the low-frequency signal component f ₀ in the optical signal after the time-division separation processing, and the low-frequency oscillators 93-1 and 9-3
Based on the phase difference between the low frequency signal f ₀ component from 3-2, a clock signal supplied to the optical switches 92-1 and 92-2, the operation of the optical switches 92-1 and 92-2 An operation point stabilization control circuit for controlling the operation point on the characteristic to be a fixed position is configured.

With the above-described configuration, in the optical time division demultiplexing apparatus according to the ninth embodiment of the present invention, the polarization demultiplexing section 91 performs bi-polarization components (input optical time division multiplexed signals) of the received optical signal (optical time division multiplexed signal). (TE wave, TM wave). Also,
In each of the optical switches 92-1 and 92-2, the clock signal generator 21-1 converts the optical time-division multiplexed signal (TE wave and TM wave), which has been polarization-separated into two by the wavelength separator 91, respectively. , 21-2, are subjected to the same optical time-division separation processing as in the above-described embodiments, and then multiplexed by the optical multiplexing unit 99.

[0208] The optical signal multiplexed by the optical multiplexing unit 99 is input to the polarization splitter 83 via the optical splitter 95, and is again split into two polarization components by the polarization splitter 83. Furthermore, optical signals (TE wave, TM wave) separated into two polarization components
Are converted into electric signals by the photodetectors 96-1 and 96-2, respectively, and output to the band-pass filters 97-1 and 97-2.

The band pass filter 97-1 detects the frequency f ₀ component contained in the output optical signals from the light receivers 96-1 and 96-2. When the bandpass filter 97-1 detects the frequency f ₀ component, the optical switch 92
At -1, an operating point drift has occurred. In this case, in the phase detection / bias supply circuit 98-1, the low-frequency signal f ₀ from the band-pass filter 97-1 is used.
The operating point drift is detected by comparing the phase of the low frequency signal f ₀ from the low frequency oscillator 93-1 with the phase.

Further, a phase detection / bias supply circuit 98
-1, a DC bias voltage based on the amount of this operating point drift is generated, and the
The output is superimposed on the clock signal from the drive circuit 94-1. Similarly, the band-pass filter 97-2 detects the frequency f ₀ component included in the output optical signal from the light receiver 96-2. Frequency f in bandpass filter 97-2
_{When the zero} component is detected, an operating point drift has occurred in the optical switch 92-2.

Also in this case, in the phase detection / bias supply circuit 98-2, the band-pass filter 97-
By performing a low-frequency signal f ₀ from 2 phase comparison of the low-frequency signal f ₀ from the low frequency oscillator 93-2 to detect the operating point drift. Further, in the phase detection / bias supply circuit 98-2, a DC bias voltage based on the amount of the operating point drift is generated, and the optical switch 92-2 is generated.
Is superimposed on the clock signal from the drive circuit 94-2 and output.

Thus, each of the optical switches 92-1 and 92-2
At -2, a DC bias voltage is applied to the clock signal as a drive signal in accordance with the detected operating point drift, and the operating points on the operating characteristics of the optical switches 92-1 and 92-2 become fixed positions. Is controlled as follows. As described above, also in the optical time division demultiplexing apparatus according to the ninth embodiment of the present invention, the clock signal generators 21-1, 21-2, the polarization demultiplexer 91, the optical switches 92-1 and 92-2, and the optical multiplexers 92-1 and 92-2. And a predetermined low-frequency signal f ₀ that is set in advance on a clock signal for optical time division separation supplied to each of the optical switches 92-1 and 92-2. A low-frequency signal component f ₀ in the optical signal after time-division separation processing by the optical switches 92-1 and 92-2,
Low frequency signals f ₀ from low frequency oscillators 93-1 and 93-2.
Based on the phase difference between the optical switches 92-1 and 92-1.
The clock signal supplied to the optical switch 9
Since the operating points on the operating characteristics of 2-1 and 92-2 can be controlled to be fixed positions, a polarization-independent optical time-division demultiplexing device can be configured, and each optical switch can be controlled. 92-1 and 92-2 can share the components of the feedback system for performing operating point compensation, and can reduce the number of times of light branching. This has the advantage that the cost can be reduced.

In the ninth embodiment, the polarization-independent optical time-division demultiplexing device is configured using a 1 × 1 Mach-Zehnder optical switch. However, the present invention is not limited to this. As shown in FIG. 20, a 1 × 2 Mach-Zehnder optical switch can be used, and needless to say, the same advantages as in the case of the ninth embodiment can be obtained in this case.

The optical time division demultiplexing device 90A shown in FIG.
In the above, two 1 × 2 Mach-Zehnder optical switches 92A-1 and 92A-2 are provided on the waveguide substrate, and before and after these optical switches 92A-1 and 92A-2 (input / output side).
The polarization splitters 85 and 86 are formed in the same manner as in the above-described ninth embodiment. A clock signal generator, a low-frequency oscillator, a driving circuit, an optical splitter, a polarization splitter, a light receiver, a band-pass filter, and a phase A detection / bias supply circuit can be provided (not shown in FIG. 20).

Here, in the polarization splitter 85,
A polarization separation unit 91 having the same function as that shown in FIG. 19 is provided, and one polarization separation light (TE
A wave plate (λ / 2 plate) 87-1 for converting the wave into a TM light is inserted in a stage preceding the optical switch 92A-1. Also,
The polarization splitter 86 includes two multiplexing sections 99 for multiplexing the output lights of the optical switches 92A-1 and 92A-2, as in the case of the ninth embodiment described above, and also includes a multiplexing section 99 for multiplexing the output lights of the optical switches 92A-2. A wave plate (λ / 2 plate) 87-2 for converting TM light into TE light with respect to the two output lights is inserted before the optical multiplexing unit 99. The two multiplexing sections 99 output complementary signals.

In FIG. 20, 88 is a signal electrode,
89 is an earth electrode. Thereby, each optical switch 9
A clock signal for optical time division separation processing (for example, 20) supplied to each signal electrode 88 of 2A-1 and 92A-2.
GHz), a predetermined low-frequency signal f ₀ set in advance is superimposed by a low-frequency oscillator (not shown), and the low-frequency signal in the optical signal after time-division separation processing by each of the optical switches 92A-1 and 92A-2. the component f _0, based on the phase difference between the components of the low-frequency signal f ₀ from the low-frequency oscillator described above, a clock signal supplied to the optical switches 92A-1,92A-2, the optical switches 92A- 1,92A-2
It can be controlled so that the operating point on the operating characteristic of the above becomes a fixed position.

In this case, any one of the four output signals from the two optical multiplexing units 99 is used to stabilize the operating point in each of the optical switches 92A-1 and 92A-2. The optical switches 92A-1 and 92A-2 can be used in common for control.
Operating point stabilization control can be performed simultaneously. (J) Description of Tenth Embodiment FIG. 21 is a block diagram showing an optical time division demultiplexer according to a tenth embodiment of the present invention. The optical time division demultiplexer 20B shown in FIG. As in the case of the embodiment, the present invention can be applied to an optical receiver that performs optical time division multiplexing / demultiplexing on an optical time division multiplexed signal from the optical transmitter 102 in the optical time division multiplexing transmission system as shown in FIG.

Here, the optical time-division demultiplexing device 20B according to the tenth embodiment is different from the optical time-division demultiplexing device according to the third embodiment in that it is used as an extraction bit sequence switching unit for switching a bit sequence to be extracted after time-division separation in an optical switch. And the other configuration is basically the same. In other words, in the optical time-division demultiplexing device according to each of the above-described embodiments, the extracted bit string is fixed by the output position.
In the optical time division demultiplexing apparatus 20B according to the tenth embodiment, a function of changing a bit string to be extracted is added. In FIG. 21, the same reference numerals as those in FIG. 8 indicate the same parts.

By the way, the optical time division demultiplexing device 20B shown in FIG. 21 also has the optical DEMUX1 shown in FIG.
By arranging them at the position of 15, the time-division separating device 20B and the identification units 116 and 117 can constitute an optical receiver. Here, the polarity inversion circuit 23A receives an operating point switching signal input from the outside when switching the bit string to be identified (extracted) by the identification units 116 and 117 to another bit string, and
The operation point on the operation characteristic of 2A is shifted by a half cycle.

More specifically, the polarity inversion circuit 23A
The operating point (Vb) on the optical output characteristic curve of the optical switch 22A shown in FIG. 39 is changed from Vb1 to Vb2 to Vb2 to Vb2.
By switching between Vb3 (inverting the polarity), the bit string extracted by the optical DEMUX is switched. With the above configuration,
Optical time division separator 20 according to a tenth embodiment of the present invention
In B, the optical time division demultiplexing process and the operating point stabilization control operation for the input optical time division multiplexed signal are performed as in the case of the third embodiment.

Here, in the polarity inversion circuit 23A,
When an operating point switching signal is input from outside, a low-frequency oscillator
23 to the drive circuit 24A.₀of
Reverse the polarity. Thereby, in the optical switch 22A
The phase of the low-frequency component contained in the branched optical signal is a half cycle
The low-pass detected by the band-pass filter 27
Frequency component f ₀Output is inverted and operation on the light output characteristic curve
Stabilization when the point (Vb) shifts by half a cycle
(See FIG. 39).

As described above, according to the optical time division demultiplexing apparatus according to the tenth embodiment of the present invention, the polarity inversion circuit 23A as an extraction bit string switching unit for switching the bit string to be extracted after time division separation in the optical switch 22A is provided. As a result, in addition to the same advantages as in the above-described third embodiment, the bit sequence to be extracted after the time-division separation processing can be arbitrarily switched, so that the receiving setting of the receiver of the optical signal is performed as necessary. There are also advantages that can be.

In the tenth embodiment described above,
Is interposed a polarity inverting circuit 23A described above between the low frequency oscillator 23 and the drive circuit 24, so as to reverse the low frequency polarity of the signal f ₀ to be output to the drive circuit 24 from the low frequency oscillator 23 However, the polarity inversion circuit 2 is not limited to this.
3A, for example, interposed between the low-frequency oscillator 23 and the phase detection / bias supply circuit 28,
8 is set so as to invert the low-frequency signal f ₀ as a phase comparison reference, or interposed, for example, between the light receiver 26 and the band-pass filter 27 to invert the low-frequency signal f ₀ from the light receiver 26. For example, the polarity of the feedback control may be reversed, such as setting to output to the band-pass filter 27.

Further, in the tenth embodiment, the polarity inversion circuit 23A for inverting the low frequency signal component is used as the extraction bit string switching unit.
A functional unit that inverts the DC bias voltage from the phase detection / bias supply circuit 28 in a circuit manner can be added as an extraction bit string switching unit. In addition, the above-mentioned tenth
In the embodiment, the case where the function of switching the extraction bit string is added to the optical time division demultiplexing device in the above-described third embodiment is described in detail. However, the present invention is not limited to this. It can be applied to a time-division separation device.

(K) Description of Eleventh Embodiment FIG. 22 is a block diagram showing an optical time division demultiplexer according to an eleventh embodiment of the present invention. The optical time division demultiplexer 130 shown in FIG. As in the above embodiments, the present invention is applied to an optical receiver that performs optical time division multiplexing and demultiplexing on an optical time division multiplex signal from the optical transmitter 102 in the optical time division multiplex transmission system as shown in FIG. Can be.

Here, the optical time division demultiplexing apparatus 130 according to the eleventh embodiment is different from the optical time division demultiplexing apparatus according to the first embodiment in that the time division between the clock signal generator 21 and the drive circuit 24 is different. The main difference lies in that an optical switch 22 is provided with a phase changer 131 as an extraction bit string switching unit for switching a bit string to be extracted after time-division separation. In FIG. 22, the same reference numerals as those in FIG. 4 denote the same parts, and a detailed description thereof will be omitted.

Further, the above-described phase changer 131 receives the gate switching signal input from the outside, delays the clock signal from the clock signal generator 21 by a half cycle, and outputs the delayed signal to the drive circuit 24. The drive circuit 24 generates and supplies a drive signal to the optical switch 22 based on the inverted clock signal from the phase changer 131.

Therefore, the above-described phase variable device 131 has a function as a clock variable unit that outputs the signal to the optical switch 22 via the drive circuit 24 by changing the component of the clock signal from the clock signal generating unit 21. doing. In the optical time division demultiplexer 130 according to the eleventh embodiment, the drive circuit 24 and the phase detection / bias supply circuit 28 supply a drive signal and a DC bias voltage to only one electrode of the optical switch 22. It has become.

With the above configuration, the optical time division demultiplexing apparatus 130 according to the eleventh embodiment of the present invention performs the optical time division demultiplexing on the input optical time division multiplexed signal as in the case of the first embodiment. Processing and operating point stabilization control operations are performed. That is, as shown in FIG. 23, when receiving the optical time division multiplexed signal a in which the bit strings “A” and “B” are optical time division multiplexed, the optical switch 22
Performs a time-division separation process on the basis of the clock signal b from the first stage and outputs a separated signal c from which the bit string “A” is extracted (in this state, no gate switching signal is input to the phase variable device 131 from the outside. ).

Here, when the phase changer 131 receives a gate switching signal for switching a bit string to be taken out from the outside, the clock signal from the clock signal generator 21 is delayed by a half cycle and output to the drive circuit 24. The clock signal b 'supplied from the drive circuit 24 to the optical switch 22 is delayed by a half cycle as compared to before the input of the gate switching signal.

As a result, the optical switch 22 performs time-division separation processing based on the clock signal b 'from the drive circuit 24, and switches the bit string to be extracted to the bit string "B" and outputs it. As described above, according to the optical time-division separation device 130 according to the eleventh embodiment of the present invention, the optical switch 2
2 has the same advantage as that of the first embodiment described above by providing the phase variable device 131 as an extraction bit string switching unit for switching the bit string to be extracted after the time division separation. Can be arbitrarily switched, so that there is also an advantage that the reception setting can be performed as required by the receiver of the optical signal.

In the phase variable device 131 according to the eleventh embodiment, the clock signal from the clock signal generator 21 is delayed by a half cycle.
The present invention is not limited to this, and may be configured to invert the clock signal from the clock signal generation unit 21. Even in this case, the same operation and effect as in the above case can be obtained.

In this case, the above-described phase changer 1
In place of the clock signal generator 31, a functional unit capable of inverting the clock signal from the clock signal generator 21 is provided based on the same gate signal as in the case of the phase changer 131 described above. A polarity inversion circuit for inverting the length is interposed between the clock signal generation unit 21 and the drive circuit 24.

Further, in the above-described eleventh embodiment, the function of switching the extraction bit string by changing the clock signal supplied to the optical switch is described in the first embodiment.
The case where the optical time division demultiplexer is added to the optical time division demultiplexer in the embodiment is described in detail, but the present invention is not limited to this, and can be applied to the optical time division demultiplexer according to each of the above-described embodiments.

(L) Description of the Twelfth Embodiment FIG. 24 is a block diagram showing an optical time division demultiplexer according to a twelfth embodiment of the present invention. The optical time division demultiplexer 132 shown in FIG. As in the above embodiments, the present invention is applied to an optical receiver that performs optical time division multiplexing and demultiplexing on an optical time division multiplex signal from the optical transmitter 102 in the optical time division multiplex transmission system as shown in FIG. Can be.

Here, the optical time division demultiplexing device 132 according to the twelfth embodiment differs from the optical time division demultiplexing device according to the eleventh embodiment in that the optical path length variable device 133 as an extraction bit string switching unit is different from the optical time division demultiplexing device. In addition, a mode of switching the bit string to be extracted after the time division separation in the optical switch 22 is different. In FIG. 24, the same reference numerals as those in FIG. 22 denote the same parts, and a detailed description thereof will be omitted.

The optical path length changer (optical path length changeover switch) 133 is inserted before the optical switch 22.
Upon receiving a gate switching signal input from the outside, the optical path is switched to an optical path that can change the optical path length of the input optical signal by one time slot. With the above-described configuration, the optical time division demultiplexing apparatus 132 according to the twelfth embodiment of the present invention performs the optical time division demultiplexing processing and the operation on the input optical time division multiplexed signal as in the case of the eleventh embodiment. A point stabilization control operation is being performed.

That is, as shown in FIG. 25, when receiving the optical time division multiplexed signal a in which the bit strings “A” and “B” are optically time division multiplexed, the optical switch 22
Performs a time-division separation process on the basis of the clock signal b from the first stage and outputs a separated signal c from which the bit string “A” is extracted (in this state, no gate switching signal is input to the phase variable device 131 from the outside. ).

Here, when the variable optical path length unit 133 receives a gate switching signal for switching a bit string extracted from the outside, the input optical time division multiplex signal changes by one time slot, and The signal is input to the optical switch 22 as a '. In this case, without changing the clock signal b supplied from the drive circuit 24 to the optical switch 22, the optical switch 22 performs time-division separation processing, thereby extracting the extracted bit sequence c ′ as the bit sequence “A”. To the bit string “B”.

As described above, according to the optical time division demultiplexing apparatus 132 according to the twelfth embodiment of the present invention, the optical switch 22
The optical path length changer 133 as an extraction bit string switching unit for switching a bit string to be extracted after time-division separation is provided, which has almost the same advantages as the above-described eleventh embodiment. The function of switching the extraction bit string by changing the optical path length as described in detail in the twelfth embodiment can be applied to the optical time division demultiplexing apparatus according to each of the above embodiments. It is.

(M) Description of the thirteenth embodiment FIG. 26 is a block diagram showing an optical time division demultiplexer according to a thirteenth embodiment of the present invention. As in the above embodiments, the present invention is applied to an optical receiver that performs optical time division multiplexing and demultiplexing on an optical time division multiplex signal from the optical transmitter 102 in the optical time division multiplex transmission system as shown in FIG. Can be.

Here, the optical time division demultiplexing apparatus 134 according to the thirteenth embodiment is different from the optical time division demultiplexing apparatus according to the fourth embodiment described above in that the time division separation between the clock signal generation unit 21 and the drive circuit 24 is different. The optical switch 22 is provided with phase changers 131-1 and 131-2 as extraction bit string switching units for switching bit strings to be extracted after time division separation in the optical switch 22, and other configurations are basically the same. is there.

FIG. 26 focuses on the function section for switching the extraction bit string in the optical time division demultiplexing apparatus 134 according to the thirteenth embodiment. The clock signal generation section 21 and the optical switches 32-1 and 32-2. And drive circuit 34
Each functional unit (reference numerals 33-1, 33-2, 36, 37-1, 37) other than -1 and 34-2 for operating point stabilization control
-2, 38-1 and 38-2) are not shown.

In the optical time division demultiplexing device 134 according to the thirteenth embodiment, the photodetector 13 receives the optical signal branched by the optical branching unit 35 and converts it into an electric signal.
5 and an identification circuit 13 for identifying the electrical signal from the light receiver 135 by the identification clock.
It has six. Note that the above-described identification clock is also generated by extracting from the received optical signal, similarly to the clock signal input to the above-described drive circuits 34-1 and 34-2.

Here, the above-mentioned phase changer 131-1 is
In response to an externally input gate switching signal, the input clock signal is inverted and output to the drive circuit 24-1. Further, the phase changer 131-2 receives the gate switching signal input from the outside, inverts the input clock signal and outputs the inverted clock signal to the driving circuit 24-2, and outputs the light at the previous stage of the optical switch 32-2. When the bit string to be taken out by optical time division separation is switched by the switch 32-1,
In synchronization with this switching timing, the phase of the clock signal input to the optical switch 32-2 is shifted by a desired amount (for example, one time slot; see time T in FIG. 27).

That is, the driving circuit 34-1 generates and supplies a driving signal to the optical switch 32-1 based on the inverted clock signal from the phase changer 131-1. Phase changer 131-
2, a drive signal for the optical switch 32-2 can be generated and supplied based on the clock signal whose phase has been shifted by a desired amount.

In this way, when the clock signal to the drive circuit 24-1 is inverted in the phase changer 131-1 and the bit sequence to be taken out by the optical time division separation by the optical switch 32-1 is switched, the phase changer 131-1 In 2 in synchronization with this, the phase of the clock signal supplied to the optical switch 32-2 is changed, and the center of the gate in the optical switch 32-2 becomes the bit center of the optical time-division separation signal from the optical switch 32-1. Thus, the shift is performed by a desired amount.

In other words, in the phase changer 131-2, when the gate switching signal is input to the above-described phase changer 131-1, the phase changer 131-2 is synchronized therewith.
Is shifted by a desired amount so that the center of the gate of the optical switch 32-2 becomes the center of the bit of the optical time-division separated signal from the optical switch 32-1 at the preceding stage. It is.

Therefore, the above-described phase changers 131-1, 1
31-2 changes a component of a clock signal from a clock signal generation unit (not shown) to thereby drive the driving circuit 34.
-1, 34-2 via the optical switches 32-1 and 32-2
And has a function as a clock variable unit for outputting to
Further, with respect to the identification clock in the identification circuit 136 at the subsequent stage, when the optical signals that are time-division separated in the optical switches 32-1 and 132-2 are switched, they are synchronized with the switching timing of the optical signal that is time-division separated. The phase is shifted by a desired amount.

With the above-described configuration, the optical time-division multiplexing device 134 according to the thirteenth embodiment of the present invention has the same configuration as the fourth embodiment (see reference numeral 31). , An optical time division separation process and an operating point stabilization control operation are performed. That is, in the optical switch 32-1, as shown in FIG. 27, the optical time-division multiplexing signal a as the input received optical signal is subjected to the optical time-division demultiplexing process generated by the drive circuit 34-1. And modulates it with a clock signal b (on which a DC bias voltage for stabilizing the operating point is superimposed), and outputs it as a separated signal c.

Similarly, in the optical switch 32-2,
As shown in FIG. 27, with respect to the output signal c from the optical switch 32-1, the clock signal d for optical time division separation processing generated by the above-described drive circuit 34-2 (DC for stabilizing the operating point) (A bias voltage is superimposed) to output as a separated signal e. The signal e that has been subjected to the time-division separation processing in this way is output to the identification circuit
At 36, data is identified by the identification clock f.

Here, in the phase changer 131-1,
When a gate switching signal for switching a bit string to be taken out from the outside is received, as shown in FIG. 28, a clock signal from a clock signal generator (not shown) is inverted and output to the driving circuit 34-1. The clock signal b 'supplied from -1 to the optical switch 32-1 is inverted as compared to before the gate switching signal is input.

Thus, the optical switch 32-1 performs time-division separation processing based on the clock signal b 'from the drive circuit 24, switches the bit string to be taken out, and outputs it as a separation signal c'. In the phase changer 131-2, the phase of the clock signal d 'supplied from the drive circuit 34-2 to the optical switch 32-2 is d (FIG. 2).
7) to d 'by the time T (or in the reverse direction, if necessary), by shifting the phase of the clock signal from the clock signal generator by a desired amount.

As a result, the optical switch 32-2 performs time-division separation processing based on the clock signal d 'from the drive circuit 34-2, so that the optical switch 32-1 performs optical time-division separation and extraction. Since the phase of the clock signal input to the optical switch 32-2 is shifted in synchronization with the timing at which the bit string switches, the optical switch 3
It is possible to prevent the center of the gate in 2-2 from deviating from the center of the bit of the input signal, and to extract a desired separated signal e '.

Further, regarding the identification clock in the identification circuit 136 at the subsequent stage, the optical switches 32-1 and 32-2 are used.
When the optical signal to be time-division-demultiplexed is switched, the phase is shifted by f 'from f (see FIG. 27) in synchronization with the switching timing of the optical signal to be time-division-separated. Thereby, when switching the bit string to be extracted by the optical time division separation processing, the phase relationship between the signal after the optical time division separation processing and the identification clock is synchronized.

As described above, according to the optical time division demultiplexing apparatus 134 according to the thirteenth embodiment of the present invention, the optical switch 22
, A phase variable unit 131-as an extraction bit string switching unit that switches a bit string to be extracted after time division separation.
By providing 1, 131-2, the bit string to be extracted after the time-division separation processing can be arbitrarily switched, so that there is an advantage that the receiving setting of the receiver of the optical signal can be performed as required.

Further, when the bit sequence to be taken out by optical time division separation is switched by the optical switch 32-1 at the preceding stage, the bit sequence is input to the optical switch 32-2 at the subsequent stage in synchronization with the switching timing of the optical signal to be time division separated. The phase of the clock signal to be shifted can be shifted by a desired amount, so that the center of the gate in the optical switch 32-2 at the subsequent stage can be prevented from being shifted from the center of the bit of the input signal. There is also an advantage that can be obtained efficiently and reliably.

When the optical signals which are time-division separated by the optical switches 34-1 and 34-2 are switched, the identification clock of the identification circuit 136 is synchronized with the switching timing of the optical signals which are time-division separated. Since the phase can be shifted by a desired amount, the phase relationship between the signal after the optical time division separation processing and the identification clock can be synchronized when switching the bit string to be extracted by the optical time division separation processing. There is an advantage that a desired bit string can be efficiently and reliably identified.

(N) Description of Fourteenth Embodiment FIG. 29 is a block diagram showing an optical time division demultiplexer according to a fourteenth embodiment of the present invention. The optical time division demultiplexer 140 shown in FIG. As in the above embodiments, the present invention is applied to an optical receiver that performs optical time division multiplexing and demultiplexing on an optical time division multiplex signal from the optical transmitter 102 in the optical time division multiplex transmission system as shown in FIG. Can be.

Here, the optical time division demultiplexing apparatus 140 according to the fourteenth embodiment has a function section for further performing an electric time division demultiplexing process at the subsequent stage of the optical time division demultiplexing apparatus in the eleventh embodiment. ing. Therefore, the optical time division demultiplexing device 140 according to the fourteenth embodiment includes the same phase variable device 131 as that of the eleventh embodiment (see reference numeral 130).

FIG. 29 shows the function of performing the above-mentioned electrical time division separation processing, together with the function of switching the extraction bit string when performing optical time division separation, with respect to the optical time division separation apparatus 140 according to the fourteenth embodiment. Part (reference numerals 135 to 1)
38, and other functional units (see numerals 23, 26 to 28) for operating point stabilization control other than the clock signal generating unit 21, the optical switch 22, and the drive circuit 24 are illustrated. Omitted.

Here, as a functional unit for performing the above-described electric time-division separation processing (electric DEMUX), a light receiving unit 135, a D-flip-flop 137, and a phase variable unit 138 are provided, and an identification circuit 136 is provided. ing. The optical receiver 135 receives the optical signal branched by the branch unit 25 and converts the optical signal into an electric signal. The D-flip-flop 137 outputs an electric signal to be described later.
The EMUX clock signal is input via the phase changer 138, and the electrical DEMUX clock signal is used as the clock timing to output the electrical signal from the optical receiver 135. A time-division separation process is performed.

It should be noted that the clock signal for the electric DEMUX is also supplied to the drive circuit 24 by the phase changer 1.
Clock signal for optical time-division separation processing input via 31 (generated by a clock signal generator (not shown))
In the same manner as described above, it is extracted and generated from the received optical time division multiplexed signal. Also, the identification circuit 136
The data subjected to the electrical DEMUX processing by the flip-flop 137 is identified by the identification clock. In addition, also about the above-mentioned identification clock,
Like the clock signals input to the drive circuits 24 and 138 described above, they are extracted and generated from the received optical signals.

Incidentally, similarly to the phase variable device 131, the phase variable device 138 receives a gate switching signal input from the outside, inverts the input clock signal, and outputs the inverted signal to the D-flip-flop 137. When the bit sequence extracted by optical time-division separation is switched by the optical switch 22 at the previous stage of the D-flip-flop 137, the phase of the electrical DEMUX clock signal input to the D-flip-flop 137 is synchronized with this switching timing. Is shifted by a desired amount (for example, one time slot; see time T in FIG. 30).

In other words, when the optical switch 22 switches the bit sequence to be extracted by the optical time division separation, the D-flip-flop 137 performs the electrical time division separation in synchronization with the switching timing of the extracted bit sequence. By shifting the phase of the clock signal at this time by a desired amount,
The identification position in the D-flip-flop 137 is set to be the bit center of the optical time-division separation signal from the optical switch 22 at the preceding stage.

Further, the phase of the discrimination clock in the discrimination circuit 136 at the subsequent stage is also synchronized with the switching timing of the above-described time-division-separated optical signal when the optical signal subjected to the optical time-division separation in the optical switch 22 is switched. It is shifted by a desired amount. With the configuration described above, the optical time-division splitting device 140 according to the fourteenth embodiment of the present invention
In the eleventh embodiment (reference numeral 130)
In the same manner as described above, the optical time division demultiplexing process and the operating point stabilization control operation are performed on the input optical time division multiplexed signal, while the D-flip-flop 137 electrically connects the signal after the optical time division demultiplexing process. After the time division separation processing is performed, the data is identified by the identification circuit 136.

That is, in the optical switch 22, FIG.
As shown in the figure, the input optical time division multiplexed signal a as the received optical signal is converted into the clock signal b for the optical time division separation processing generated by the drive circuit 34-1 (for stabilizing the operating point). Is superimposed on the DC bias voltage) and is output as a separated signal c. Similarly, in the optical switch 22, as shown in FIG. 30, the output signal c from the optical switch 22 is converted into an electric signal by the photodetector 135, and then the D-flip-flop 137 performs electric time division separation. Perform processing.

That is, in the D-flip-flop 137,
A clock signal d for electrical time division separation processing extracted from the received optical time division multiplexed signal is input via a phase variable device 138 and output as an electrical time division separation signal e. The signal e thus subjected to the time-division separation processing is identified by the identification circuit 136 by the identification clock f.

The clock signal d input to the D-flip-flop 137 has half the frequency of the clock signal b for the optical time-division separation processing. By discrimination at the (down) position, a signal having a bit rate of 1/4 of the optical time division multiplexed signal a, such as the electrical time division separation signal e, is obtained.

Here, when the phase changer 131 receives a gate switching signal for switching a bit string to be taken out from the outside, as shown in FIG. 31, a clock signal from a clock signal generator (not shown) is inverted to drive the driving circuit. 2
4, the clock signal b ′ supplied from the drive circuit 24 to the optical switch 22 is inverted as compared to before the input of the gate switching signal.

As a result, the optical switch 22 performs time-division separation processing based on the clock signal b 'from the drive circuit 24, switches the bit string to be extracted, and outputs it as a separation signal c'. In the phase changer 138, the phase of the electrical DEMUX clock signal d 'is shifted by a desired amount, for example, from d (see FIG. 30) to d' by the time T (or in the opposite direction as necessary). Let it.

As a result, the D flip-flop 137
Then, an electrical time-division separation process is performed based on the clock signal d 'whose phase has been shifted by the phase variable unit 138, so that the optical switch 22 synchronizes with the timing at which the bit sequence to be extracted by the optical time-division separation is switched. Since the phase of the clock signal input to the D-flip-flop 137 is shifted, the discrimination center of the D-flip-flop 137 is prevented from deviating from the center of the bit of the input signal, and the desired separation signal is prevented. e 'can be taken out.

Further, with respect to the discrimination clock in the discrimination circuit 136 at the subsequent stage, when the optical signal that is time-division separated in the optical switch 22 is switched, the phase is synchronized with the switching timing of the optical signal that is time-division separated as described above. (Figure 2
7) is shifted by f '. Thereby, when switching the bit string to be extracted by the optical time division separation processing, the phase relationship between the signal after the optical time division separation processing and the identification clock is synchronized.

As described above, according to the optical time division demultiplexing apparatus 140 according to the fourteenth embodiment of the present invention, the optical switch 22
, A phase variable device 131-1 as an extraction bit sequence switching unit that switches a bit sequence to be extracted after time-division separation.
With this arrangement, it is possible to arbitrarily switch the bit string to be extracted after the time-division demultiplexing process, so that there is an advantage that the receiving setting of the receiver of the optical signal can be performed as required.

Further, when the bit sequence to be taken out by optical time division separation is switched by the optical switch 22 at the preceding stage, the D-flip-flop 137 performs electrical time division synchronization in synchronization with the switching timing of the optical signal to be time division separated. Since the phase of the clock signal at the time of separation can be shifted by a desired amount, the center of identification in the D-flip-flop 137 can be prevented from shifting from the center of the bit of the input signal, and the desired optical signal can be prevented. There is also an advantage that can be obtained efficiently and reliably.

When the optical signal to be time-divisionally separated is switched by the optical switch 22, the phase of the identification clock in the identification circuit 136 is shifted by a desired amount in synchronization with the switching timing of the optical signal to be time-divisionally separated. Therefore, when switching the bit string to be extracted after being subjected to the optical time division separation processing, the phase relationship between the signal after the optical time division separation processing and the identification clock can be synchronized, so that the desired bit string can be efficiently converted. There is an advantage that identification can be performed reliably.

(O) Others As for the optical switch constituting the optical time division demultiplexing device according to each of the above-described embodiments, any one of the optical switch for applying the drive clock signal to the two electrodes and the two electrodes can be used. The present invention can be applied to any optical switch that applies a drive clock signal to only one electrode. In particular, in an optical switch that applies a drive clock signal to only one of the two electrodes,
The DC bias voltage for compensating the operating point drift is also supplied to the electrode to which the clock signal is applied.

In the optical time division demultiplexing apparatus according to each of the above embodiments, in a mode in which a drive clock signal is applied to two electrodes in an optical switch, a drive circuit that generates a drive clock signal to these two electrodes However, the present invention is not limited to this, and it is also possible to separately prepare circuits. Furthermore, in the optical time division demultiplexing apparatus according to each of the above-described embodiments, a band-pass filter is used to perform operating point stabilization control. Can also.

[0279]

As described above, claims 1, 2, 12 to 1
According to the present invention described in 4,21,22,26, the optical time division separation supplied to the optical switch such as the 1 × 1 Mach-Zehnder optical switch or the 1 × 2 Mach-Zehnder optical switch by the operating point stabilization control circuit. For processing clock signal,
A predetermined low-frequency signal set in advance by the low-frequency oscillator is superimposed, and the above-described low-frequency signal component in the optical signal after the time-division separation processing by the optical switch and the predetermined low-frequency signal set by the low-frequency oscillator are performed. The clock signal supplied to the optical switch can be controlled based on the phase difference with the component of the frequency signal so that the operating point on the operating characteristics of the optical switch is at a fixed position. about,
The optical time-division separation can be performed while compensating for the operating point drift, so that there is an advantage that a separation signal having a sufficient light output intensity can be output.

Further, according to the optical time division demultiplexer of the present invention, in the band-pass filter provided corresponding to the optical switch of the operating point stabilization control circuit,
Since a low-frequency signal can be detected from the optical signal output from the last-stage optical switch, a common branch unit for splitting the output optical signal and a photodetector that converts the split optical signal into an electrical signal are shared. Therefore, by performing the operating point stabilization control collectively by reducing the number of branches of the optical signal, it is possible to reduce the loss of monitor light, while increasing the circuit scale or mounting area. There is also an advantage that it is possible to suppress the size and reduce the size and to contribute to the cost reduction for configuring the device.

According to the optical time division demultiplexer of the present invention, the operating point of the clock signal supplied to any one of the plurality of optical switches is changed with respect to the operating characteristics of the optical switch. In order to temporally switch the control to the constant position, the switching of the first switch and the second switch is controlled, and the update of the bias voltage information held in the bias voltage holding unit is controlled. Therefore, it is possible to share the components of the feedback system for performing the operating point compensation in each optical switch,
Since the number of times of light branching can be reduced, there is an advantage that loss of monitor light as branching light can be reduced, and miniaturization of a circuit and cost reduction for configuring an apparatus can be achieved.

Further, according to the optical time division demultiplexing device of the present invention, it has a clock signal generation part, a first light demultiplexing part and an optical multiplexing part, and is supplied to each of the optical switches. A predetermined low-frequency signal set in advance is superimposed on a clock signal for optical time-division separation processing, and a low-frequency signal component in the optical signal after time-division separation processing by each optical switch, and a signal from a low-frequency oscillator. The clock signal supplied to each optical switch can be controlled based on the phase difference between the components of the low-frequency signal so that the operating point on the operating characteristic of each optical switch is at a fixed position. The components of the feedback system for performing the operating point compensation in the switch can be shared, and the number of times of light branching can be reduced, so that the loss of the optical signal is reduced,
There is an advantage that the circuit size can be reduced and the cost for configuring the device can be reduced.

According to the optical time division demultiplexing apparatus of the present invention, the first optical demultiplexing unit is configured to demultiplex the wavelength multiplex component in the input signal light. There is an advantage that an optical time division demultiplexing device that performs an optical time division demultiplexing process on an optical time division multiplexed signal that has been processed can be configured. Claims 10 and 11
According to the described optical time division demultiplexing apparatus of the present invention, the first optical demultiplexing unit is configured to separate the two polarization components in the input signal light, and the optical multiplexing unit and the low frequency signal detecting unit are separated from each other. Since the second optical demultiplexing unit for separating the two polarization components in the optical signal multiplexed by the optical multiplexing unit is interposed therebetween, a polarization independent optical time division demultiplexing device is configured. There are advantages that can be.

According to the optical time division demultiplexing device of the present invention, the extraction bit sequence switching section for switching the bit sequence to be extracted after the time division demultiplexing in the optical switch allows the bit sequence to be extracted after the time division demultiplexing process. Since the switching can be performed arbitrarily, there is an advantage that the reception setting can be performed according to the needs of the receiver of the optical signal.

Further, according to the separation signal switching method of the present invention, when a bit string that is optically time-division-separated and extracted is switched by an optical switch, it is synchronized with the switching timing of the optical signal to be time-division-separated. Since the phase of the clock signal input to the subsequent optical switch can be shifted by a desired amount, it is possible to prevent the center of the gate in another optical switch from being shifted from the center of the bit of the input signal. There is also an advantage that a desired optical signal can be efficiently and reliably obtained.

According to the separation signal switching method of the present invention, when the bit sequence that is extracted by the optical time division by the optical switch is switched, it is synchronized with the switching timing of the optical signal to be time division separated. Therefore, the phase of the clock signal at the time of performing the electrical time division separation can be shifted by a desired amount, so that the identification center at the time of performing the electrical time division separation is prevented from being shifted from the center of the bit of the input signal. There is also an advantage that a desired optical signal can be efficiently and reliably obtained.

Further, according to the separation signal switching method of the present invention, when an optical signal that is time-division separated by an optical switch is switched, it is synchronized with the switching timing of the time-division separated optical signal. Therefore, the phase of the identification clock for data identification can be shifted by a desired amount. Therefore, when switching the bit string to be taken out by the optical time division separation processing, the signal after the optical time division separation processing and the identification clock are switched. Since the phase relationship can be synchronized, there is an advantage that a desired bit string can be efficiently and reliably identified.

[Brief description of the drawings]

FIG. 1 is a principle block diagram of the present invention.

FIG. 2 is a principle block diagram of the present invention.

FIG. 3 is a principle block diagram of the present invention.

FIG. 4 is a block diagram showing an optical time-division splitting device according to the first embodiment of the present invention.

FIG. 5 is a block diagram illustrating a main part of the optical time-division separation device according to the first embodiment of the present invention.

FIG. 6 is a diagram for explaining an operation of the optical time-division splitting device according to the first embodiment of the present invention.

FIG. 7 is a block diagram showing a main part of an optical receiver to which an optical time division demultiplexing device according to a second embodiment of the present invention is applied.

FIG. 8 is a block diagram showing an optical time division demultiplexer according to a third embodiment of the present invention.

FIG. 9 is a block diagram showing an optical time-division splitting device according to a fourth embodiment of the present invention.

FIG. 10 is a block diagram showing an optical receiver to which an optical time division demultiplexing device according to a fourth embodiment is applied.

FIG. 11 is a time chart for explaining an operation of the optical time-division separation device according to the fourth embodiment of the present invention.

FIG. 12 is a block diagram showing an optical time division demultiplexer according to a fifth embodiment of the present invention.

FIG. 13 is a time chart for explaining the operation of the optical time-division separation device according to the fifth embodiment of the present invention.

FIG. 14 is a block diagram showing an optical time division demultiplexer according to a sixth embodiment of the present invention.

FIG. 15 is a block diagram showing an optical time division demultiplexer according to a seventh embodiment of the present invention.

FIG. 16 is a block diagram showing a main part of an optical time division demultiplexing apparatus according to a seventh embodiment of the present invention.

FIG. 17 is a block diagram showing an optical time division demultiplexer according to an eighth embodiment of the present invention.

FIG. 18 is a block diagram showing an optical time division demultiplexer according to a modification of the eighth embodiment of the present invention.

FIG. 19 is a block diagram showing an optical time division demultiplexer according to a ninth embodiment of the present invention.

FIG. 20 is a diagram illustrating an optical time-division separation device according to a modification of the ninth embodiment of the present invention.

FIG. 21 is a block diagram showing an optical time division demultiplexer according to a tenth embodiment of the present invention.

FIG. 22 is a block diagram showing an optical time division demultiplexer according to an eleventh embodiment of the present invention.

FIG. 23 is a time chart for explaining the operation of the optical time-division separation device according to the eleventh embodiment of the present invention.

FIG. 24 is a block diagram showing an optical time division demultiplexer according to a twelfth embodiment of the present invention.

FIG. 25 is a time chart for explaining an operation of the optical time-division separation device according to the twelfth embodiment of the present invention.

FIG. 26 is a block diagram showing an optical time division demultiplexer according to a thirteenth embodiment of the present invention.

FIG. 27 is a time chart for explaining an operation of the optical time-division separation device according to the thirteenth embodiment of the present invention.

FIG. 28 is a time chart for explaining the operation of the optical time-division separation device according to the thirteenth embodiment of the present invention.

FIG. 29 is a block diagram showing an optical time-division splitting device according to a fourteenth embodiment of the present invention.

FIG. 30 is a time chart for explaining the operation of the optical time-division separation device according to the fourteenth embodiment of the present invention.

FIG. 31 is a time chart for explaining the operation of the optical time-division separation device according to the fourteenth embodiment of the present invention.

FIG. 32 is a block diagram showing an optical transmission / reception system employing an optical time division multiplexing / demultiplexing method.

FIG. 33 is a block diagram showing a main part of the optical transmitting and receiving system shown in FIG. 32;

FIG. 34 is a block diagram showing a main part of the optical transmission / reception system shown in FIG.

FIG. 35 is a time chart for explaining the operation of the optical transmitting and receiving system shown in FIG. 32;

FIG. 36 is a block diagram illustrating a main part of the optical transmission and reception system illustrated in FIG. 32;

FIG. 37 is a block diagram showing a main part of the optical transmission / reception system shown in FIG. 32.

FIG. 38 is a time chart for explaining the operation of the optical transmitting and receiving system shown in FIG. 32;

FIG. 39 is a diagram showing an optical output characteristic with respect to a drive voltage of a Mach-Zehnder optical switch.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Optical time division | separation apparatus 2 Clock signal generation part 3 Optical switch 4 Operating point stabilization control circuit 5 Optical time division | separation apparatus 6 Clock signal generation part 7-1-7-n Optical switch 8 Operating point stabilization control circuit 9 Light Time division demultiplexer 10 Clock signal generator 11 First optical demultiplexer 12-1 to 12-n Optical switch 13 Optical multiplexer 14 Operating point stabilization control circuit 20, 20A, 20B Optical time division demultiplexer 21 Clock signal generator 22, 22A Optical switch 22a, 22b Electrode 23 Low frequency oscillator 23A Polarity inversion circuit (extraction bit string switching unit) 24, 24A Drive circuit (low frequency superposition unit) 25 Optical branching unit 26 Optical receiver 27 Bandpass filter (Low frequency signal detection 28) Phase detection / bias supply circuit (bias voltage supply unit) 28a Inverting full-wave rectifier 28b Low-pass filter 29,2 A Operating point stabilization control circuit 30-1 to 30-m Optical DEMUX 31 Optical time division demultiplexing device 32-1, 32-2 Optical switch 33-1, 33-2 Low frequency oscillator 34-1, 34-2 Drive circuit (Low-frequency superimposing unit) 35 Optical branching unit 36 Optical receiver 37-1, 37-2 Band-pass filter (Low-frequency signal detection unit) 38-1, 38-2 Phase detection / bias supply circuit (Bias voltage supply unit) 40 Optical time-division separation device 42-1 to 42-3 Optical switch 43-1 to 43-3 Low-frequency oscillator 44-1 to 44-3 Drive circuit (low-frequency superimposing unit) 45 Optical branching unit 46 Optical receiver 47-1 47-3 Band Pass Filter (Low Frequency Signal Detection Unit) 48-1 to 48-3 Phase Detection and Bias Supply Circuit (Bias Voltage Supply Unit) 50 Optical Time Division Separation Device 52-1 to 52-3 Optical Switch 53-1 ~ 53 3 Low Frequency Oscillator 54-1 to 54-3 Drive Circuit (Low Frequency Superposition Unit) 55-1 and 55-2 Optical Branching Unit 56-1 and 56-2 Light Receiver 57-1 to 57-3 Band Pass Filter (Low Frequency signal detection unit) 58-1 to 58-3 Phase detection / bias supply circuit (bias voltage supply unit) 60 Optical time-division separation device 61-1 First switch 61-2 Second switch 62-1 to 62- Reference Signs List 3 optical switch 63 low-frequency oscillator 64-1 to 64-3 drive circuit (low-frequency superimposing section) 65 optical branching section 66 photodetector 67 band-pass filter (low-frequency signal detecting section) 68A phase detecting circuit (phase difference detecting section) 68B-1 to 68B-3 Bias holding circuit (bias voltage holding unit) 69a Integrating circuit 69a-1 OP amplifier 69a-2 Capacitor 69a-3, 69a-4 Resistance 69a-5 to 69a- Switch 69b Voltage follower 69b-1 Resistor 69b-1 69b-2 OP amplifier 71 Wavelength separation unit 72-1,72-2 Optical switch 73,73-1,73-2 Low frequency oscillator 74-1,74-2 Drive circuit (Low-frequency superposition unit) 75 Optical branching unit 76 Optical receiver 77, 77-1, 77-2 Band-pass filter (Low-frequency signal detection unit) 78-1, 78-2 Phase detection / bias supply circuit (Bias voltage supply unit) 78A phase detection circuit (phase difference detection unit) 78B-1, 78B-2 bias holding circuit (bias voltage holding unit) 79 optical multiplexing unit 80, 80 'optical time division demultiplexing device 81-1 first changeover switch 81-2 Second changeover switch 82 Oscillator circuit 83 Polarization separation element 85, 86 Polarization splitter 87-1, 87-2 Delay element 88 Signal electrode 89 Ground electrode 90 90A Optical time-division demultiplexing device 91 Polarization separation unit 92-1 and 92-2 Optical switch 92A-1 and 92A-2 Optical switch 93-1 and 93-2 Low-frequency oscillator 94-1 and 94-2 Drive circuit (low Frequency superimposing section) 95 Optical branching section 96-1, 96-2 Light receiver 97-1, 97-2 Bandpass filter (low frequency signal detecting section) 98-1, 98-2 Phase detection / bias supply circuit (bias voltage) Supply unit) 99 Optical multiplexing unit 100 Optical transmission / reception system 101 Transmission line 102 Optical transmitter 103 Optical receiver 104, 105 Optical modulation unit 106 Optical time division multiplexing unit 106a Laser diode 106b Modulation unit 106c Oscillator 106d Branch unit 106e Delay unit 106f, 106g Modulation section 106h Combining section 107, 107A Optical branching section 108, 109 Optical DEMUX 110, 111 Identification section 12 1 × 1 Mach-Zehnder type optical switch 112a, 112b Electrode 113 Drive circuit 114 Optical receiver 115 Optical DEMUX 116, 117 Identification unit 118 1 × 2 Mach-Zehnder type optical switch 118a, 118b Electrode 119 Drive circuit 121 Optical branching unit 122-1 to 12-1 122-4 Optical DEMUX 123-1 to 123-4 Identification Unit 130 Optical Time Division Separator 131 Phase Variable (Clock Variable Unit) 132 Optical Time Division Separator 133 Optical Path Length Variable Device 134 Optical Time Division Separator 135 Optical Receiver 136 Identification circuit 137 D-flip-flop 138 Phase changer 139 Optical time-division separation device

Claims (26)

[Claims] 1. A clock signal generator for generating a clock signal for optical time-division separation processing of a received optical signal, and an optical switch for time-division separating an optical signal based on the clock signal from the clock signal generator. An optical time-division demultiplexing device, comprising: superimposing a predetermined low-frequency signal on a clock signal for the optical time-division demultiplexing process supplied to the optical switch; Based on the phase difference between the predetermined low-frequency signal component in the optical signal after the time-division demultiplexing process and the component of the predetermined low-frequency signal set,
An optical switch comprising an operating point stabilization control circuit for controlling a clock signal supplied to the optical switch so that an operating point on operating characteristics of the optical switch is kept at a fixed position. Split separation equipment. 2. An operating point stabilization control circuit comprising: a low-frequency oscillator for generating a predetermined low-frequency signal; a low-frequency oscillator for generating a low-frequency signal from the low-frequency oscillator; A low-frequency superimposing unit that superimposes a frequency signal and outputs it as a clock signal to the optical switch; a low-frequency signal detecting unit that detects the low-frequency signal included in the optical signal time-division-divided by the optical switch; Applying a bias voltage corresponding to a difference between the phase of the low-frequency signal from the low-frequency oscillator and the phase of the low-frequency signal detected by the low-frequency signal detector to the optical switch; The optical time-division splitting device according to claim 1, further comprising a supply unit. 3. A clock signal generator for generating a clock signal for optical time division separation processing of a received optical signal, and an optical switch for time division separating an optical signal based on the clock signal from the clock signal generator. A plurality of stages, and an optical time-division demultiplexing device that performs time-division demultiplexing on an input optical signal a plurality of times, wherein the clock signal for optical time-division demultiplexing supplied to each optical switch is While superimposing the set predetermined low-frequency signal, the position of the predetermined low-frequency signal component and the set predetermined low-frequency signal component in the optical signal after the time-division separation processing by each optical switch is performed. An operating point stabilization control circuit for controlling a clock signal supplied to each optical switch based on the phase difference so that an operating point on the operating characteristic of each optical switch becomes a fixed position. Wherein the optical time division demultiplexing apparatus. 4. An operating point stabilization control circuit comprising: a low-frequency oscillator for generating predetermined low-frequency signals different from each other; and a predetermined low-frequency signal from the low-frequency oscillator, A low-frequency superimposing unit that superimposes a signal and outputs the signal as a clock signal to the optical switch; a low-frequency signal detecting unit that detects the low-frequency signal from the optical signal output from the last-stage optical switch; A bias voltage supply unit that applies a bias voltage corresponding to a difference between the phase of the low-frequency signal from the oscillator and the phase of the low-frequency signal detected by the low-frequency signal detection unit to the optical switch; 4. The optical time-division separation device according to claim 3, wherein the optical time-division separation device is provided for each of the optical switches. 5. An operating point stabilization control circuit, comprising: a low-frequency oscillator for generating a predetermined low-frequency signal; and detecting the low-frequency signal from an optical signal output from the last-stage optical switch. A low-frequency signal detector, a phase difference detector that detects a phase difference between the low-frequency signal from the low-frequency oscillator and the low-frequency signal detected by the low-frequency signal detector, A low-frequency superimposing unit that is provided for each optical switch in each stage and superimposes the low-frequency signal from the low-frequency oscillator on the clock signal from the clock signal generating unit; A bias voltage holding unit that can temporarily hold a bias voltage corresponding to the phase difference detection information from the phase difference detection unit; and the low frequency signal from the low frequency oscillator, and a low frequency superposition unit of each stage. Selectively cut to any of A first changeover switch for alternately outputting, and a second changeover switch for selectively switching and outputting the phase difference detection information from the phase difference detection section to one of the bias voltage holding sections of each stage. In order to perform control by switching the operating point of the clock signal supplied to any of the plurality of optical switches to a fixed position with respect to the operating characteristics of the optical switch, the first switch and the first switch 4. The optical time division separation according to claim 3, wherein the switching of the second changeover switch is controlled, and the bias voltage information held by the bias voltage holding unit is controlled to be updated. apparatus. 6. A clock signal generator for generating a clock signal for optical time division separation of a received optical signal, a first optical separator for separating the input signal light into a plurality of optical signals, A plurality of optical switches that time-division-divides the optical signal separated by the first optical separation unit based on the first optical separation unit; and an optical multiplexing unit that multiplexes the optical signals that are time-division separated by the plurality of optical switches. An optical time-division demultiplexing device comprising: a predetermined low-frequency signal superimposed on a clock signal for the optical time-division demultiplexing process supplied to each of the optical switches; A clock supplied to each optical switch based on a phase difference between the predetermined low-frequency signal component in the optical signal after the time-division separation processing by each optical switch and the set predetermined low-frequency signal component. The signal is sent to each optical switch. Wherein the operating point of the operational characteristics is configured to include the operating point stabilization control circuit is controlled to be constant position of the optical time division demultiplexing apparatus. 7. An operating point stabilization control unit comprising: a low-frequency oscillator for generating predetermined low-frequency signals different from each other; and a clock signal from the clock signal generation unit, and a predetermined low-frequency signal from the low-frequency oscillator. A low-frequency superimposing unit that superimposes a signal, a low-frequency signal detecting unit that detects the low-frequency signal from the optical signal multiplexed by the optical multiplexing unit, and a phase of the low-frequency signal from the low-frequency oscillator. A bias voltage supply unit for applying a bias voltage corresponding to a difference between the phase of the low frequency signal detected by the low frequency signal detection unit and the optical switch to the optical switch, for each of the plurality of optical switches; The optical time-division separation device according to claim 6, wherein the device is configured as follows. 8. An operating point stabilization control section, comprising: a low frequency oscillator for generating a predetermined low frequency signal set in advance; and detecting the low frequency signal from the optical signal multiplexed by the optical multiplexing section. A low-frequency signal detecting unit that performs a light-emitting operation on the optical signal by applying a bias voltage corresponding to a difference between a phase of the low-frequency signal from the low-frequency oscillator and a phase of the low-frequency signal detected by the low-frequency signal detecting unit to the light; A bias voltage supply unit applied to the switch; and a low frequency superimposing unit provided for each of the plurality of optical switches, and superimposing the low frequency signal from the low frequency oscillator on the clock signal from the clock signal generating unit. And a bias voltage holding unit that is provided for each of the plurality of optical switches and temporarily holds the bias voltage information from the bias voltage supply unit, while the low frequency signal from the low frequency oscillator is , The plurality of low A first changeover switch for selectively switching and outputting to any of the frequency superimposing units; and selectively applying the bias voltage from the bias voltage supply unit to any of the plurality of bias voltage holding units. A second changeover switch for switching and outputting the bias signal such that the operating point of the clock signal supplied to any of the plurality of optical switches is at a fixed position with respect to the operating characteristics of the optical switch. It is configured to control the switching of the first switch and the second switch so that the bias voltage is supplied from the voltage supply unit, and to control the update of the bias voltage information from the bias voltage holding unit. 7. The optical time-division separation device according to claim 6, wherein: 9. The optical time-division demultiplexing device according to claim 6, wherein said first optical demultiplexing unit is configured to demultiplex a wavelength division multiplex component in said input signal light. 10. The optical time-division splitting device according to claim 6, wherein the first optical splitting unit is configured to split the two polarization components in the input signal light. 11. A second light separating unit is provided between the optical multiplexing unit and the low-frequency signal detecting unit for separating two polarization components in the optical signal multiplexed by the optical multiplexing unit. The optical time-division separation device according to claim 10, wherein: 12. The optical switch based on a difference between a phase of a low-frequency signal from the low-frequency oscillator and a phase of the low-frequency signal detected by the low-frequency signal detector. And detecting a drift of the operating characteristic of the optical switch, and supplying a bias voltage such that the operating point of the clock signal supplied to the optical switch is at a fixed position with respect to the operating characteristic. , Claims 2, 4, 5,
The optical time-division separation device according to any one of claims 7 and 8. 13. The optical switch according to claim 1, wherein the bias voltage supply unit is configured to detect a difference between a phase of the low frequency signal detected by the low frequency signal detection unit and a phase of the low frequency signal from the low frequency oscillator. A drift detection unit that detects a drift of the operation characteristic; and a bias voltage application unit that applies a bias voltage corresponding to the drift detected by the drift detection unit to a clock signal supplied to the optical switch in a superimposed manner. 13. The optical time-division separation device according to claim 12, wherein the optical time-division separation device is provided. 14. A low-frequency signal detection device, comprising: a branching unit that branches an optical signal output from the optical switch; and a photoelectric conversion unit that converts the optical signal branched by the branching unit into an electric signal. The unit is configured by a band-pass filter capable of passing the predetermined low-frequency component of the electric signal from the photoelectric conversion unit, wherein
The optical time-division separation device according to any one of 4, 5, 7, and 8. 15. The optical time-division demultiplexing device according to claim 1, further comprising an extraction bit sequence switching unit for switching a bit sequence extracted in a time-division manner in said optical switch. 16. The optical time division demultiplexing apparatus according to claim 15, wherein said take-out bit string switching unit is configured to shift an operating point on an operating characteristic of said optical switch by a half cycle. 17. The output bit string switching unit comprises a clock variable unit that changes a component of the clock signal from the clock signal generation unit and outputs the component to the optical switch. The optical time-division separation device according to the above. 18. The optical time division demultiplexer according to claim 17, wherein said clock variable unit is configured to be able to invert said clock signal from said clock signal generation unit. 19. The optical time division demultiplexer according to claim 17, wherein said clock variable section is configured to delay said clock signal from said clock signal generation section by a half cycle. 20. The take-out bit string switching section is constituted by an optical path length switch inserted before the optical switch and capable of switching to an optical path capable of changing the optical path length of the input optical signal by one time slot. The optical time-division separation device according to claim 15, wherein: 21. The optical time-division demultiplexing device according to claim 1, wherein said optical switch comprises a one-input one-output Mach-Zehnder optical switch. 22. The optical time-division demultiplexing device according to claim 1, wherein said optical switch comprises a one-input two-output Mach-Zehnder optical switch. 23. A separation signal switching method for switching a signal to be output in a time division manner when an input optical signal is subjected to optical time division separation based on a clock signal in a plurality of optical switches. When the bit sequence extracted by optical time division separation is switched, the phase of a clock signal input to another optical switch is shifted by a desired amount in synchronization with the switching timing of the optical signal subjected to time division separation. , A separated signal switching method. 24. An input optical signal is optically time-division-separated by an optical switch, converted into an electric signal, and then, when electrically time-division-separated based on a clock signal, output after time-division separation. In the separation signal switching method for switching signals, when a bit string to be extracted by optical time division separation is switched by the optical switch, a clock signal for performing the electrical time division separation in synchronization with the switching timing of the extracted bit string. Wherein the phase is shifted by a desired amount. 25. A separation signal switching method for switching the signal to be time-division-separated and identified at the time of data identification by an identification clock after the input optical signal is optically time-division-separated by an optical switch and converted into an electric signal. In the above, when the optical signal that is time-division separated by the optical switch is switched, the phase of the identification clock is shifted by a desired amount in synchronization with the switching timing of the optical signal that is time-division separated. Separation signal switching method. 26. An excitation light source for outputting excitation light, a low-frequency oscillator for generating a predetermined low-frequency signal,
An input clock and a data signal, a low-frequency superimposing unit that superimposes the low-frequency signal from the low-frequency oscillator, and excitation light from the excitation light source, the low-frequency signal is superimposed by the low-frequency superimposing unit. An optical switch for performing time-division multiplexing modulation based on a clock and a data signal for transmission; And applying a bias voltage corresponding to the difference between the phase of the low-frequency signal from the low-frequency oscillator and the phase of the low-frequency signal detected by the low-frequency signal detection unit to the optical switch. An optical time division multiplexing device having a bias voltage supply unit; a clock signal generation unit for generating a clock signal for optical time division separation of a received optical signal; and a predetermined low frequency signal generated in advance. A low-frequency oscillator, a low-frequency superimposing section for superimposing the low-frequency signal from the low-frequency oscillator on the clock signal from the clock signal generating section, and the low-frequency signal is superimposed on the low-frequency superimposing section. An optical switch that time-division-divides the input optical signal based on the clock signal, a low-frequency signal detection unit that detects the low-frequency signal included in the optical signal that is time-division-divided by the optical switch, A bias voltage supply for applying a bias voltage corresponding to a difference between the phase of the low-frequency signal from the low-frequency oscillator and the phase of the low-frequency signal detected by the low-frequency signal detector to the optical switch. An optical time-division multiplexing transmission system comprising an optical time-division demultiplexing device having a unit.